Modal verbs and their use in English

Post date: Mar 13, 2015 6:03:10 PM

1. What are modal verbs?

Modal verbs are auxiliary verbs that are never used alone except as question tags like any other auxiliary verb. Which means that:

• They are followed by a base infinitive --> can read

• They are used with not in negative sentences --> I will not read

• They precede the subject in questions --> can you read?

2. Which modal verbs are there?

• must

• will

• would

• can

• could

• may

• might

• shall

• should

• mustn't

There are also some modal phrases:

• ought to

• needn't

Some other phrases are used as substitutes to certain modal verbs BUT they are not modal verbs:

• have to

• be able to

• be allowed to

3. Use of modal verbs to express probability, possibility or certainty

Possibility:

We use the modals could, might and may to show that something is possible in the future, but not certain:

They might come later. (= Perhaps/Maybe they will come later.)

They may come by car. (= Perhaps/Maybe they will come by car.)

If we don’t hurry we could be late. (= Perhaps/Maybe we will be late)

We use could have, might have and may have to show that something was possible now or at some time in the past:

It’s ten o’clock. They might have arrived now.

They could have arrived hours ago.

We use the modal can to make general statements about what is possible:

It can be very cold in winter. (= It is sometimes very cold in winter)

You can easily lose your way in the dark. (= People often lose their way in the dark)

We use the modal could as the past tense of can:

It could be very cold in winter. (= Sometimes it was very cold in winter.)

You could lose your way in the dark. (= People often lost their way in the dark)

Impossibility:

We use the negative can’t or cannot to show that something is impossible:

That can’t be true.

You cannot be serious.

We use couldn’t/could not to talk about the past:

We knew it could not be true.

He was obviously joking. He could not be serious.

Probability:

We use the modal must to show we are sure something to be true and we have reasons for our belief:

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

You haven’t eaten all day. You must be hungry.

We use must have for the past:

They have not eaten all day. They must have been hungry.

You look happy. You must have heard the good news.

We use the modal should to suggest that something is true or will be true in the future, and to show you have reasons for your suggestion:

Ask Miranda. She should know.

It's nearly six o'clock. They should arrive soon.

We use should have to talk about the past:

It's nearly eleven o'clock. They should have arrived by now.

4. Use of modal verbs to express ability, permission, request or advice

Ability:

We use can to talk about someone’s skill or general abilities:

She can speak several languages.

He can swim like a fish.

They can’t dance very well.

We use can to talk about the ability to do something at a given time in the present or future:

You can make a lot of money if you are lucky.

Help. I can’t breathe.

They can run but they can’t hide.

We use could to talk about past time:

She could speak several languages.

They couldn’t dance very well.

We use could have to say that someone had the ability/opportunity to do something, but did not do it:

She could have learned Swahili, but she didn’t have time.

I could have danced all night [but didn't].

Permission:

We use can to ask for permission to do something:

Can I ask a question, please?

Can we go home now.

could is more formal and polite than can:

Could I ask a question please?

Could we go home now?

may is another more formal and polite way of asking for permission:

May I ask a question please?

May we go home now?

We use can to give permission:

You can go home now if you like.

You can borrow my pen if you like.

may is a more formal and polite way of giving permission:

You may go home now, if you like.

We use can to say that someone has permission to do something:

We can go out whenever we want.

Students can travel free.

may is a more formal and polite way of saying that someone has permission:

Students may travel free.

Instructions and requests:

We use could you and would you as polite ways of telling or asking someone to do something:

Could you take a message please?

Would you carry this for me please?

Could I have my bill please?

can and will are less polite:

Can you take a message please?

Will you carry this for me please?

Suggestions and advice:

We use should to make suggestions and give advice:

You should send an email.

We should go by train.

We use could to make suggestions:

We could meet at the weekend.

You could eat out tonight.

We use conditionals to give advice:

Dan will help you if you ask him.

Past tenses are more polite:

Dan would help you if you asked him.

Offers and invitations:

We use can I… and to make offers:

Can I help you?

Can I do that for you?

We can also use shall I …

Shall I help you with that?

Shall I call you on your mobile?

We sometime say I can ... or I could ... or I’ll (I will) ... to make an offer:

I can do that for you if you like.

I can give you a lift to the station.

I’ll do that for you if you like.

I’ll give you a lift to the station.

We use would you like (to) ... for invitations:

Would you like to come round to morrow?

Would you like another drink?

We use you must or we must for a very polite invitation:

You must come round and see us.

We must meet again soon.

We use modal verbs to say how sure we are about something.

must

We use must when we feel sure that something is true because there’s very strong evidence.

• • He must live near here because he comes to work on foot. We do not know where he lives but we’re sure it’s not far away.

  • Come inside and get warm – you must be freezing out there.

  • You’re a zookeeper? That must be very interesting.

might, may, could

We use might, may or could to say that we think something is possible but we’re not sure.

• • Did you hear that? I think there might be a burglar downstairs. She’s not sure there’s a burglar but she thinks it’s possible.

  • We’ll try to get there early but we may arrive late if there’s a lot of traffic.

  • Don’t put it up there. It could fall off and hit someone.

can’t

We use can’t when we feel sure something is not true.

• • It can’t be a burglar. All the doors and windows are locked. He does not know it’s not a burglar but he feels sure it’s not.

  • It can’t be far away now. We’ve been driving for hours. Where’s the map?

  • Really? He has to work on Christmas Day? He can’t feel very happy about that.

6. Deduction and speculation (past)

In the same way that we use modal verbs to say how certain we are about things in the present we can also use them to speculate about the past.

must + perfect infinitive

We use must + perfect infinitive when we feel sure about something in the past.

• • You must have been delighted when you heard you’d won the lottery.

  • The thieves must have come in through the window. Look – it’s still open.

  • Oh no! Where’s my car? Someone must have stolen it!

might/may/could + perfect infinitive

We use might, may or could with the perfect infinitive to say that we think something was possible but we are not sure.

• • The thieves might have escaped by car but we can’t be sure.

  • He should be hour by now. He may have been delayed by a traffic jam or something.

  • I can’t find my purse. I could have left it in the supermarket but I just don’t know.

can’t + perfect infinitive

We use can’t + perfect infinitive when we feel sure something did not happen in the past.

• • I thought I saw John in town this morning but it can’t have been him – he’s in Greece this week.

  • I can’t have left it in the supermarket – I had it on the bus on the way home.

  • You can’t have read the instructions properly. They’re perfectly clear.