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How To Use Modal Verbs In English (The Complete Guide)

Modal verbs in English can be confusing! In this guide, we’ll explain what they are, why and how we use them correctly, and give you examples to improve your understanding. Mastering modals like should, would, may and might will help you express yourself clearly in the English. Don’t forget to download the pdf so you can study more at home!

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What you will learn:


What are modal verbs?

Modal verbs allow us to express ideas and opinions connected with possibility, certainty, necessity, ability, obligation or the willingness to do something. Common modal verbs include: can, should and must. For example, in ‘I must go home’ the modal verb ‘must’ shows obligation.

Modals are a type of auxiliary (helping) verb. Sometimes we can use a normal auxiliary verb and a preposition to express the same idea. For example, in ‘I have to go home’ this combination means the same as ‘must’. We call this a “semi-modal”.

Some important differences between modals and other verbs are:

  1. Modal verbs cannot be used without main verbs in positive or negative sentences and questions
    • I can give you the answer tomorrow morning. – Right
    • I can ___ the answer tomorrow morning. – Wrong
  2. For he/she/it forms, modals do not add ‘-s’
    • He should tell his mother. – Right
    • He shoulds tell his mother. – Wrong
  3. After a modal verb, you always use the infinitive (main verb, but without ‘to’)
    • We might go to the cinema this evening. – Right
    • We might to go to the cinema this evening. – Wrong
  4. Questions with modal verbs are easy because you just invert the subject and modal
    • I should vs. Should I go?


How many modal verbs are there in English?

English has 9 modal verbs: can, could, may, might, must, shall, should, will, would.

As we mentioned above, there are also some semi-modals that can be used to express the same thing as modal verbs. Common examples are: have to, need to, able to and ought to.

There are many different ways of using the 9 modal verbs in English. In this guide, we will show you how to use them to express your ideas and opinions.

Why do we use modal verbs?

We can use modal verbs for a variety of purposes. We have summarised their main uses for you below.

  • You can make your speech and writing more polite by using modal verbs.
    • If you want to send a letter, we can draft it for you. (more direct)
    • If you would like to send a letter, we will be happy to draft it for you. (more polite)
  • You can give your opinion on the likelihood of something happening.
    • It will / may / might / should / could rain this afternoon. (degrees of likelihood)
  • You can show how certain you are about something that has happened.
    • It was John’s mistake that lost us the contract. (fact)
    • It could / might / must / can’t have been John’s mistake. (levels of certainty)
  • You can sound more polite when making offers or requests.
    • I want to open the window. (not asking permission)
    • Can / May / Shall I open the window? (asking if it is alright to do it)
    • Could / would you open the window, please? (asking somebody to do it) 
  • With modal verbs, you can express more complex ideas.
    • I might / may / should / will / should have got that job. (degrees of certainty)
    • I might / could / must / should / will / may go to see the film tomorrow. (different possibilities)
    • My family could / might / may / should be coming to see me at the weekend. (some doubt)


6 types of modal verbs (with examples)

When we say “types” here, we really mean “modalities” – this is where the term ‘modal verb’ comes from. A modality is a specific way of doing or experiencing something. Some modals are flexible and can be used to express several different modalities, but others are limited to just one or two situations. Let’s take a look!

1. Modals of Ability – can, could

The Merriam Webster Learner’s Dictionary says that ability is the power or skill to do something. There are two ways we can use modals to express ability – in the present and in the past. Quite simply, can is used to talk about things in present time, and could is when we want to talk about the past. So, we have present and past ability. Here are some examples of ability modals in use:

Present ability: Paul can play the piano very well.
Present ability negative: You can’t sing and you can’t dance either!

Past ability: When you were a child, you could read long books.
Past ability negative: I couldn’t ride a bicycle until I was 5 years old.

What about modals of ability in the future? Well, for this we do not use can or could. Instead, we need to use the semi-modal able to, and often this is used together with will. For example: 

Future ability: I am learning guitar and soon I will be able to play my favourite songs.
Future ability negative: She does not practise much, so she won’t be able to win her next match.

A common mistake is to use an infinitive after a modal verb. Don’t do it! We must instead only use the base form of the verb.
I must to go to London tomorrow. (Wrong)
I must go to London tomorrow. (Right)

2. Modals of Advice & Suggestion – should, could, might, would, shall

Merriam Webster defines advice to be an opinion or suggestion about what someone should do, while the Macmillan Dictionary says that suggestion is an idea or plan that you offer for someone to consider.

For giving advice, we most commonly use the modal verb should. However, we can also use could or might, though giving advice this way is less strong. Using would to give advice is more abstract or hypothetical, as in: What would you do if you won the lottery? We can sometimes use shall, but only in questions.

Here are some examples:

Present advice / suggestion:

  • You really should give up smoking!
  • Tonight we could go to see a film or to a restaurant.
  • It might be a good idea to phone them before we go there.
  • If I were you, I would take an umbrella when you go out tonight.

Present advice / suggestion negative:

  • He shouldn’t eat so many chocolate because it will make him fat.
  • You might not want to go to the party because your ex will be there.
  • Couldn’t you phone them again just to make sure they are at home?
  • I wouldn’t go there if I were you. It’s a dangerous part of town!

Present advice / suggestion question:

  • Should I stay at home or go to the party with George?
  • Shall we have a barbecue sometime next week?
  • Could you ask your dad to help with your homework?

We can also use the semi-modals ought to and had better to give advice. Ought to is similar in meaning to should, but had better is for much stronger advice. Some examples of these in use are:

Present advice: It’s very cold today, and you really ought to wear a scarf and gloves.
Present advice: You are driving much too fast! I think you had better slow down!
Present advice negative: You had better not waste any more time on your ex-boyfriend!

Remember that we don’t use the -ing form of the verb after a modal. Instead, we have to use the base form.

We can’t going to the cinema next week. (Wrong)

We can’t go to the cinema next week. (Right)

3. Modals of Deduction – must, may, might, could, can’t

Merriam Webster says that deduction is a conclusion or opinion that is based on logic or reason. However, there are different ways to say how sure we are, and we can be more or less certain that what we are talking about is true. So, we need to use different modals of deduction to show this:

  • We use must when there is very strong evidence that something is true
  • We use might, may or could to say we think something is possible, but we don’t know for sure. There is some disagreement between native speakers on the “order of certainty” that these modals should be in, but most would agree that:
    • May suggests: more possibly yes
    • Might suggests: more possibly no
    • May is used more formally than might or could
    • Could is the most commonly used of the three, and you should use might when you are less sure
  • We use can’t when there is very strong evidence that something isn’t true

Here are some modals of deduction examples:

Present deduction:

  • This must be her house. I can see her car in the garage.
  • Robert could be at the library now. He has an exam tomorrow.
  • George may be stuck on the motorway in traffic.
  • She might go to the cinema with you tonight if you ask her.

Present deduction negative:

  • You have been sleeping all day so you can’t be tired now!
4. Modals of Obligation & Prohibition – must, should, can’t

Merriam Webster says that obligation is something that you must do because of a law, rule, promise, etc. On the other hand, prohibition is the act of not allowing something to be used or done.

There are two types of obligation – strong obligation using must and recommendation or moral obligation where we use should. And with prohibition, we use can’t for when it is strong, and shouldn’t for times when it is “recommended not to”.

It is also worth saying that there are semi-modal verb forms that we can use here. We can use have to in a similar way to must, and the semi-modal ought to can be used in the way that we use should. However, there are some important differences:

Present obligation with must / have to

Despite what many grammar books tell you, there is almost no difference in meaning between must and have to in the positive form. Yes, many grammar sources talk about internal and external obligation, but these are interchangeable and the strong obligation is the same.

  • You must / have to be over 18 to buy alcohol in this town.
  • I must / have to go to bed early tonight as I have an exam in the morning.

In the negative form, and with prohibition, this is where there is a very clear difference between the two. In fact, mustn’t and don’t have to are almost opposite in their meanings. Mustn’t is a way to express strong prohibition, whereas don’t have to shows there is a complete lack of obligation.

  • You mustn’t smoke in the house. (100% do not do it!)
  • You don’t have to stay here if you don’t want to. (Go if you want to, but there’s no pressure to stay or to go)

We can’t use two modal verbs together, one after the other. Instead, we use a semi-modal.

He won’t can meet us at work in the morning. (Wrong)

He won’t be able to meet us at work in the morning. (Right)

Present obligation with should / ought to 

It is not so common these days to hear somebody using ought to, and it is a rather formal way to express obligation. As far as differences go, ought to shows a slightly stronger obligation than should, but generally speaking we use should much more often.

  • You really should / ought to go and see the doctor if you feel so ill.
  • I think you should / ought to go and say sorry because you upset Tim last night.

Present prohibition with should / ought to

It is even less common to use ought to in the negative form. It is grammatically possible, but the construction is a little wordy and awkward.

  • You shouldn’t / ought not to go to work today if you feel so ill.
  • You shouldn’t / ought not to do things like that. People don’t like it!

Present prohibition with can’t

It is also possible to use can’t to express prohibition, though it is not as strong as when you use mustn’t. We also tend to use can’t to talk more about something that is not possible. Let’s contrast these two sentences:

  • You can’t go out tonight. You’ve got homework to do for school tomorrow!
  • You mustn’t go out tonight. You’ve got homework to do for school tomorrow!

Obligations and prohibitions in the past

Again here, some semi-modals come into use – especially when using the past form of must.

  • Must (present) → had to (past)
  • Should (present) → should have (past)
  • Don’t have to (present) → didn’t have to (past)
  • Shouldn’t (present) → shouldn’t have (past)
  • Can’t (present) → couldn’t (past)
5. Modals of Permission – can, may, might, could, must

Permission, says the Macmillan dictionary, is the right to do something that is given to you by someone in authority. Can and may are the most commonly used modal verbs when asking for permission. May is used much less these days and sounds politer and more formal.

  • You can go out when you’ve finished your dinner.
  • Can I borrow your car at the weekend, Dad?
  • Use a black pen to complete the form, but you may also use a blue pen if you do not have one.
  • May I ask what your full name is, please?

Using might for permission is possible, but it is very rarely used outside formal situations, and even then is used only in questions. Might I can also be used to make a suggestion in a very formal and polite way. Some people think of might as a more formal version of may.

  • Might I recommend the grilled salmon fillet to go with your white wine? (posh, formal)

We can also use must not or mustn’t to talk about permission. Of course, this is when we are not giving permission. These modals are more formal and are often used on signs and in official announcements.

  • Passengers must not speak to the driver while the bus is moving.
  • You mustn’t smoke in this restaurant – it is not allowed here!
  • Children under 10 must not use the swimming pool without adult supervision.

In addition, we use could to ask for permission, and it is a more formal version of can.

  • Could I have some more orange juice, please?

To talk about permission in the past, we can only use the modal verb could. But it is also possible to use semi-modal forms in the past:

  • Can (present) → could (past)
  • May / might (present) → was / were allowed to (past)

Some examples of this in use:

  • Both staff and students could use the ice rink.
  • We couldn’t study in the library after 6pm.
  • I couldn’t ask any questions until the end of the lecture.
  • Although I was a little too young, I was allowed to enter the race.
  • My tutor’s name was Robert, but we were allowed to call him Rob.

Similarly, we can also use these semi-modals to talk about the present:

  • I’m sorry sir, you are not allowed to go backstage without a pass.
  • My dog is not allowed to jump up or sit on the sofa.

Be careful when using modal verbs in the negative form. Avoid using don’t and didn’t.

I don’t should drink so much coffee at work. (Wrong)

I shouldn’t drink so much coffee at work. (Right)

6. Modals of Possibility & Probability – could, may, might, should, must, will, can

The Macmillan Dictionary says that possibility is the chance that something might happen or be true, and that probability is a measure of how likely something is to happen.

This is probably the most common use of modal verbs, and all modals can express these two functions in some way.

In terms of common usage, it is the 7 above that we are mainly concerned with here. We can order them in this way:

  • Could, may, mightmaybe
  • Should this is probably true
  • MustI’m pretty sure this is true
  • Will → I’m very sure this is true
  • Canthis is generally possible 

Remember that can is not used to talk about specific events:

  • Where’s Paul? I’m not sure. He may / might / could be in his office. (NOT can!)

Here is another subtle difference between can and may / might / could:

  • Dogs can be dangerous. = Sometimes dogs are dangerous, but not usually
  • That dog may / might / could be dangerous. = it’s possible the dog is dangerous, we don’t know for sure, be careful

We also use can’t or cannot when we talk about things that are impossible (in our opinion):

  • That can’t be true!
  • You cannot be serious!

We use must to say we are sure something is true and we have reasons to believe this:

  • It’s getting dark. It must be quite late already.
  • You haven’t eaten all day. You must be hungry.

We use should when we want to suggest that something is true and we have reasons to believe this:

  • Ask my mother about that. She should know the answer.
  • It’s nearly 6 o’clock. The train should be here soon.

Last of all, we use will when we are quite sure that something is true because we know that this is how it normally happens:

  • It’s 10 o’clock so she’ll be at work by now.
  • The bus will be here in the next five minutes, so don’t worry!

Here are a few more examples of modals of possibility and probability:

  • I can’t find my keys. They must be here somewhere – I had them this morning!
  • This may be the last time I come to this bar – I’m leaving town tomorrow.
  • Elvis Presley can’t be alive. Someone would have seen him by now.
  • She might come this evening, but she said she had some work to finish first.
  • Alice is quite conservative. She may not like that pink wallpaper!


Modal verbs in the past, future and passive

Modals in the past (Perfect Modals) – could, should, might, may, must, can, would

We can use modal verbs to talk about the past and what has happened or what we think happened. The form we use to talk about modal verbs in the past is:

MODAL VERB +  have  +  3rd FORM OF VERB (past participle)

For modals of obligation and prohibition, we have the following:

  • Must (present) → had to (past)
  • Don’t have to (present) → didn’t have to (past)
  • Can’t (present) → couldn’t (past)

Let’s look at some examples of past forms of modals with the other modalities:

  • We should have taken the bus, but we decided to walk.
  • You could have listened to me, but you decided not to!
  • You might have caught a taxi as I suggested, but instead you decided to walk.
  • Diana must have forgotten about our lunch date because she is not here.
  • Julia may have been in an accident because I heard about it on the radio.
  • You can’t have been at work today because your car was in the garage all day!
  • How did she fail that exam? She can’t have studied very much.
  • Leila was hungry, but she didn’t eat very much. She mustn’t have liked the food.
  • He might not have received the message because he hasn’t replied yet.
  • I wouldn’t have called if I had known you were asleep.
  • I shouldn’t have shouted at you yesterday. I’m sorry. I was very upset!
Modal verbs in future tenses

We have looked at the most common ways of using modals in the present and past as support for the main verbs. But let’s not forget about future forms, which also involve modals as much as the others.

All modals can be used to refer to future time in some way or another. Take a look at these examples:

  • I must go and see the doctor soon
    • Maybe the decision was made at the time of speaking, but the appointment with the doctor is coming soon.
  • Will you still love me when I’m old and grey?
    • The speaker wants an answer to his/her question now, but the sentence refers to some time in the (distant) future.
  • We should get somebody to come and fix our shower.
    • Again, decision made now, but it’s unclear when the person is coming to do the job.
  • We might have to sell the car if you lose your job!
    • Maybe the car will stay, maybe not. But for now they have it, though in the future maybe not!
  • You would need to take an exam before you started this job.
    • The job has not started yet, and it can’t start if the listener doesn’t do the exam soon.

The problem with modal verbs in the future is that we need other verbs to “help” them. This is because we cannot have two modals together in the same sentence. To solve this problem, we need to use a semi-modal:

  • She will be able to type very fast when she finishes her course.
  • It will be possible to cross the river when they fix the bridge.
  • I would be allowed to drink alcohol if I was an adult.
  • We must be allowed to talk to the Prime Minister before we leave!
  • It won’t be possible to return your books when the library is closed.
  • The company should be able to finish the building work by Christmas.
  • If I may be permitted to bring in another witness to the court, then we can continue.
  • If you are quick, it might be possible to get your letter posted on time.

Finally, here are some more examples of future tense forms used together with will:

  • I think I will go to a movie tonight.
    • The decision in the present decides an action in the future.
  • I will be starting my guitar lessons tomorrow.
    • This statement in the present tells us when a future action starts.
  • I will have arrived at my office by the time you finish your breakfast.
    • Tells us about an action that completes by a future time.
  • I will have been writing for hours when my father gets back from the office.
    • Tells us how much time an action will have taken by a certain time.
Passive voice modals

With modals in the passive voice, we have present and past forms:

  • Present tense forms: modal be  +  3rd form of the verb (past participle)
  • Past tense forms: modal +  have been  +  3rd form of the verb (past participle)

Let’s look at some examples of the passive with modal verbs in the present tense:

  • The bill must be paid before leaving the restaurant.
  • You will be told which room the exam is in today.
  • The central heating should be fixed by the end of the day.
  • The candidates can be given detailed information about the new job.

Here are some more examples of modals in the passive voice in the past tense:

  • The letters should have been sent out by now.
  • You may not have understood what he was trying to tell you yesterday.
  • These books should have been studied carefully before the exam!
  • That necklace is not in the shop window so it must have been sold.

We spoke previously about the future uses of modal verbs, and we can do this with passive voice modals too:

  • The car must be taken back to the garage after the test drive.
  • These sandwiches will be sold by the end of the day.
  • Bicycles may be ridden on this bike path again from next week.
  • Something should be done about the noise from the neighbours next door.
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Download: This blog post is available as a convenient and portable PDF that you can take anywhere. Click here to get a copy. (Download)

Written by Alex Jude —
ESL Specialist & CEO at Online Teachers UK

Alex Jude is the Founder & CEO of Online Teachers UK. He holds a BA hons degree in Linguistics from The University of Manchester and is a life-long English teacher. Following graduation, he spent 2002-2012 living and teaching in Russia, where he lectured in General Linguistics and Translation Studies. Alex is a fluent Russian speaker and worked with the BBC at the World Cup in 2018. In his spare time, he enjoys camping/bushcraft, playing guitar and watching rugby league.

Written by Alex Jude —
ESL Specialist & CEO at Online Teachers UK