MODAL verbs

Modal verbs are used before other verbs to add extra meaning to a sentence, for example, obligation or permission. 

Some common modal verbs are:

1. Will

2. Would

3. Should and Ought to

4. Could

5. May

6. Can

7. Shall

8. Must

9. Might

Modal verbs share the following characteristics:

• We put an infinitive without to after most modal verbs: She should study harder.

• Modals do not take -s in the third person: I can ride a motorbike. He can ride a motorbike, too.

• Modals do not use the auxiliary do / does to form negatives, questions or short answers: She shouldn’t eat so much cheese.

1 We use can and can’t to say what we are able and not able to do in the present. 

We use could and couldn’t in the past.

I can’t use a tablet computer.

We use be able to in all tenses and after other modal verbs.

I’ll be able to meet you tomorrow.

2 We use can and could in requests. Could is usually more polite.

Can I leave now?

Could you lend me a pen, please?

1 In affirmative sentences, we can use must, need to and have to (need to and have to are not modal verbs) to describe obligation and necessity.

Students must answer the questions honestly.

2 In negative sentences, we use don’t have to, don’t need to or needn’t when there is a lack of necessity and no obligation (when you can choose how to behave).

We don’t have to / needn’t / don’t need to wear a uniform.

However, when we describe things that are not allowed (prohibition), we use mustn’t.

You mustn’t skip breakfast every day.

3 We can also use can’t to refuse a request.

You can’t go out until you’ve finished your homework.

4 We use ought to and should to give advice and make recommendations. Ought to is more formal than should.

You ought to / should apply for the job.

You ought not to / shouldn’t go out if you’re ill.

1 We use may, may not, might, might not and could when something is possible.

She might choose Jacob, not Edward.

May vs. might

May and might may seem interchangeable, but they aren’t. These are the key differences between them:

May:

• Used most often in the present tense

• Used to describe a probable hypothetical

• Can be used to give or ask for permission

Might:

• Used most often in the past tense

• Used to describe unlikely hypotheticals

• Used to describe situations that did not occur

2 We use must when we are certain something is true and can’t when we are certain something is impossible.

It must be quite late because it’s getting dark.

It can’t be midnight already!

1 We form modal perfects with a modal verb + have + past participle.

He might have phoned her last night.

2 We use modal perfects to speculate about and make deductions about past actions.

3 We use must have and can’t have to express certainty in the past.

Dad must have felt disappointed when he lost.

It can’t have been Rachael – she was in London.

4 We use might have, may have or could have to express a possibility in the past.

Tim might / may / could have gone to the cinema.

5 We also use could have to suggest an alternative past action.

The police could have acted more quickly.

6 We use should have when we regret not doing something. 

We should have gone cycling while it was sunny.

7 We use shouldn’t have when we think the person did the wrong thing.

I shouldn’t have stayed out so late last night.