Modal Verbs in English: Uses, Examples and Exercises

What are modal verbs?

Modal verbs work with a main verb to add meaning related to ability, possibility, obligation, permission, advice or deduction.

They have several unusual grammar rules.

Use the base form after a modal verb

She can drive.

We should wait.

He might know the answer.

Do not use to before the main verb.

Incorrect:

You should to study more.

Correct:

You should study more.

Modal verbs do not change with the subject

I can swim.

He can swim.

They can swim.

There is no third-person -s.

Incorrect:

She cans speak French.

Correct:

She can speak French.

Form negatives with not

Place not after the modal verb.

You must not enter.

She might not agree.

We should not worry.

Common contractions include:

cannot → can’t
could not → couldn’t
should not → shouldn’t
must not → mustn’t
would not → wouldn’t

Form questions by moving the modal before the subject

Can you help me?

Should we leave now?

Might they arrive early?

Do not use do or does with a modal verb.

Incorrect:

Do you can swim?

Correct:

Can you swim?

Ability: can and could

Use can to describe present ability.

I can speak Mandarin.

She can run five kilometres.

He cannot drive.

Use could to describe general ability in the past.

I could swim when I was five.

My grandfather could speak four languages.

For one successful action in a particular past situation, was able to or managed to is often more natural.

The door was locked, but we managed to open it.

The firefighters were able to rescue everyone.

Use can or could to ask whether something is possible.

Can you come to the meeting?

Could you finish this by Friday?

In this use, could often sounds more polite or less direct.

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Possibility: may, might and could

Use may, might or could when something is possible but not certain.

It may rain later.

She might be at home.

The delay could cause problems.

These modal verbs often have similar meanings. Might can suggest slightly less certainty than may, but the difference is often small.

We may go to the beach tomorrow.

We might go to the beach tomorrow.

Use may not or might not when something is possibly not true.

He may not know about the change.

They might not arrive on time.

Be careful with could not. It often means something was impossible rather than possibly untrue.

She couldn’t attend the meeting.

This normally means she was unable to attend.

For uncertain future situations, use:

She might not attend the meeting.

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Obligation: must, have to and should

Must

Use must for strong obligation, rules or something the speaker considers necessary.

You must wear a seat belt.

I must remember to call Daniel.

Visitors must show identification.

The negative form must not means something is prohibited.

You must not smoke here.

Employees must not share their passwords.

Have to

Use have to for obligations caused by rules, circumstances or another person.

I have to submit the form by Friday.

She has to wear a uniform at work.

In many situations, must and have to have similar meanings:

You must complete the application.

You have to complete the application.

However, have to changes for tense and subject:

He has to leave.

We had to wait.

They will have to apply again.

There is no normal past form of must for obligation, so use had to.

I had to work late yesterday.

Do not have to versus must not

These structures have very different meanings.

You do not have to attend.

Attendance is optional.

You must not attend.

Attendance is prohibited.

Should

Use should for advice, recommendations or weaker obligation.

You should drink more water.

We should leave before the traffic gets worse.

People should respect the rules.

Should not means something is not advisable.

You should not drive when you are tired.

Modal verbs can also be used in passive structures, such as The form must be completed. Learn how to build these sentences in our complete passive voice guide.

Permission and requests

Use can, could and may to ask for permission.

Can I use your phone?

Could I leave a little early?

May I ask a question?

May is more formal, while can is extremely common in everyday English.

To give permission, use can or may.

You can leave now.

Students may use a dictionary during the test.

To refuse permission, use cannot, may not or a clearer negative expression.

You cannot park here.

Visitors may not enter this area.

Use can, could and would for requests.

Can you open the window?

Could you send me the document?

Would you help me move this table?

Could and would generally sound more polite than can.

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Advice and deduction

Advice

Use should or ought to to give advice.

You should speak to your manager.

He ought to apologise.

Use shouldn’t or ought not to for negative advice.

You shouldn’t ignore the problem.

For stronger advice, use must:

You must try this restaurant.

Here, must expresses an enthusiastic recommendation rather than an official rule.

Deduction

Modal verbs can show how certain we are about a conclusion.

Use must when you believe something is almost certainly true.

She has been working all day. She must be tired.

The lights are on, so someone must be home.

Use can’t when you believe something is impossible.

He can’t be at work. I just saw him at the station.

This can’t be the correct address.

Use may, might or could when something is possible.

They might be stuck in traffic.

She may know the answer.

It could be a technical problem.

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Modal verbs in the past

To discuss past possibilities, deductions, criticism or regret, use:

modal + have + past participle

Past possibility

She may have missed the train.

They might have forgotten the meeting.

The email could have gone into your spam folder.

These sentences describe possible explanations for past events.

Past deduction

Use must have for a strong conclusion about the past.

The ground is wet. It must have rained.

He knew every answer, so he must have studied carefully.

Use can’t have or couldn’t have when a past event seems impossible.

She can’t have sent the message because her phone was broken.

They couldn’t have arrived before us.

Past advice and criticism

Use should have + past participle for an action that would have been better.

You should have told me earlier.

I should have studied more.

Use should not have for an action that was a mistake.

He shouldn’t have spoken to her like that.

Unnecessary past actions

Use need not have + past participle when an action happened but was unnecessary.

You needn’t have brought any food. We had plenty.

Compare:

You didn’t need to bring any food.

This may mean you did not bring it because it was unnecessary.

You needn’t have brought any food.

This means you brought it, but it was unnecessary.

Modal forms can change when another person’s words are reported. For example, will often becomes would and can often becomes could. See our guide to reported speech for the complete rules.

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Common mistakes

Adding to after a modal verb

Incorrect:

She can to help us.

Correct:

She can help us.

Adding third-person -s

Incorrect:

He musts leave now.

Correct:

He must leave now.

Using do in modal questions

Incorrect:

Do we should wait?

Correct:

Should we wait?

Confusing must not and do not have to

Incorrect when something is optional:

You must not come tomorrow.

Correct:

You do not have to come tomorrow.

Using must for past obligation

Incorrect:

I must work late yesterday.

Correct:

I had to work late yesterday.

Using can for uncertain possibility in affirmative statements

Less natural:

It can rain later.

Better for a specific uncertain prediction:

It may rain later.

It might rain later.

Can is more common for general possibility:

Winters can be very cold here.

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Exercises and answers

Complete each sentence with the most suitable modal verb or modal structure.

1. My sister __________ play the piano very well. (present ability)
2. You __________ show your passport at immigration. (strong obligation)
3. It __________ rain later, so take an umbrella. (possibility)
4. You __________ use your phone during the exam. (prohibition)
5. We __________ wear a uniform; it is optional. (no necessity)
6. __________ you help me carry this box? (polite request)
7. He worked for twelve hours. He __________ be exhausted. (deduction)
8. She __________ be at home, but I’m not certain. (possibility)
9. I __________ swim when I was six. (past general ability)
10. We __________ leave earlier yesterday because of the storm. (past obligation)
11. You look unwell. You __________ see a doctor. (advice)
12. They are already in Paris, so they __________ be at the meeting here. (impossibility)
13. She has not arrived. She __________ have missed the bus. (past possibility)
14. I forgot the deadline. I __________ have written it down. (past criticism)
15. The door was locked, but we __________ get inside through a window. (successful past action)

Answers and explanations

1. can
   Use can for present ability.
2. must / have to
   Both can express obligation. Must sounds particularly strong.
3. may / might / could
   All three can express uncertain future possibility.
4. must not / mustn’t
   Must not expresses prohibition.
5. do not have to / don’t have to
   The uniform is optional rather than prohibited.
6. Could / Can / Would
   All can form requests, although could and would sound more polite.
7. must
   The evidence leads to a strong present deduction.
8. may / might / could
   The speaker is uncertain.
9. could
   Use could for general ability in the past.
10. had to
    Use had to for past obligation.
11. should / ought to
    Both forms give advice.
12. can’t / cannot
    Use can’t for a conclusion that something is impossible.
13. may / might / could
    Use modal + have + past participle for a possible past explanation.
14. should
    Should have written expresses regret or criticism about the past.
15. managed to / were able to
    These forms are preferred for one successful action in a particular past situation.

Modal verbs help speakers express much more than simple actions. Use them to show ability, possibility, permission, obligation, advice and certainty. Remember that modal verbs are followed by the base form, do not take a third-person -s, and form questions without do or does.

Related grammar lessons

• Passive Voice: Rules, Examples and Exercises
• Reported Speech: Rules, Examples and Exercises
• Present Simple Tense: Rules and Exercises