Modal Verbs


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We use 'can' to talk about 'possibility'.

• Can you do that?
• I can't manage to do that.
• You can leave your car in that parking space.
• You cannot smoke in here.

Notice that there are two negative forms: 'can't' and 'cannot'. These mean exactly the same thing. When we are speaking, we usually say 'can't'.

We use 'can' to talk about 'ability'.

• I can speak English fluently.
• I can't drive a car.

We use 'can' to ask for and give permission. (We also use 'may' for this but is more formal and much less common.)

• Can I speak to you or are you too busy?
• You can use my phone.
• You can't come in.

We use 'can' in offers, requests and instructions.

• Can I help?
• Can you give me a hand?
• When you finish that, you can take out the garbage.

We use 'can' with 'see' 'hear' 'feel' 'smell' 'taste' to talk about something which is happening now . (Where you would use the present continuous with most other verbs.)

• I can smell something burning.
• Can you hear that noise?
• I can't see anything.

We can use 'can't' for deduction. The opposite of 'can't' in this context is 'must'..

• He was in London one hour ago when I spoke to him. He can't be here yet.
• You can't be hungry. You've just eaten.
• You must be hungry. You haven't eaten anything all day.


'Could' can be used to talk about the past, the present or the future.
'Could' is a past form of 'can'

• When I was living in Singapore, I could walk to work.
• He phoned to say he couldn't come.
• I could see him clearly but I couldn't hear him and then the videoconference line went dead.

'Could' is used to make polite requests. We can also use 'can' for these but 'could' is more polite.

• Could you help me, please?
• Could you lend me some money?
• Could I have a lift?
• Could I bother you for a moment?

If we use 'could' in reply to these requests, it suggests that we do not really want to do it. If you agree to the request, it is better to say 'can'

• Of course I can.
• I could help you if it's really necessary but I'm really busy right now.
• I could lend you some money but I'd need it back tomorrow without fail.
• I could give you a lift as far as Birmingham.

'Could' is used to talk about theoretical possibility and is similar in meaning to 'might'.

• It could rain later. Take an umbrella.
• He could be there by now.
• Could he be any happier?
• It could be Sarah's


We can use 'may' to ask for permission. However this is rather formal and not used very often in modern spoken English.

• May I leave now?
• May I borrow your car?
• May we think about it until tomorrow?

We use 'may' to suggest something is possible.

• John may come to stay with us
• I may not have time to do it straightaway.
• It may snow later today.

We use 'might' to suggest a small possibility of something. Often we read that 'might' suggests a smaller possibility that 'may', there is in fact little difference and 'might is more usual than 'may' in spoken English.

• It might rain this afternoon.
• She might be at home by now but it's not sure at all.
• I might not have time to go to the shops for you.
• I might not go.
For the past, we use 'might have'.

• He might have tried to call you while you were out.
• I might have left it in the taxi.


We use 'should' for giving advice.

• You should speak to him about it.
• You should see a doctor.
• You should ask a lawyer.

We use 'should' to give an opinion or a recommendation.

• We should invest more in China.
• They should do something about this terrible train service.
• He should resign.

'Should' expresses a personal opinion and is much weaker and more personal than 'must' or 'have to'. It is often introduced by ' I think'.

• I think they should replace him.
• I don't think they should keep the contract.
• Do you think I should tell her?


- We can use 'must' to show that we are certain something is true. We are making a logical deduction based upon some clear evidence or reason.

• There's no heating on. You must be freezing.
• I can't remember what I did with it. I must be getting old.

- We also use 'must' to express a strong obligation. When we use 'must' this usually means that some personal circumstance makes the obligation necessary.

• I must go to bed earlier.
• You must come and see us some time.

- We can also use 'have to' to express a strong obligation. When we use 'have to' this usually means that some external circumstance makes the obligation necessary.

• I have to arrive at work at 9 sharp. My boss is very strict.
• You have to pass your exams or the university will not accept you.

- In British English, we often use 'have got to' to mean the same as 'have to'.

• I've got to take this book back to the library or I'll get a fine.
• We've got to finish now as somebody else needs this room.

- We can also use ' will have to' to talk about strong obligations. Like 'must' this usually means that that some personal circumstance makes the obligation necessary. (Remember that 'will' is often used to show 'willingness'.)

• I'll have to speak to him.
• We'll have to have lunch and catch up on all the gossip.
** As you can see, the differences between the present forms are sometimes very small and very subtle. However, there is a huge difference in the negative forms.

We use "mustn't" to express strong obligations NOT to do something.
• I mustn't eat chocolate. It's bad for me.
• You mustn't phone me at work. We aren't allowed personal calls.

We use "don't have to" (or "haven't got to" in British English) to state that there is NO obligation or necessity.
• You don't have to come if you don't want to.

mình có bài tập về modal verb đây mọi n` cùng làm nhá:
dựa vào n~ tình huống sau để hoàn thành n~ câu sau với các từ gợi ý trong ngoặc:
1.You don't understan the lesson.
Pay /attention/ what/ teacher/say/(ought to)
2.I'm not good at english
3.He doesn't understan the proplem
Speak/him/it/today/(have to)
4.I can't phone Mary
Write/ her/letter/(ought to)
5.The child is crying
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