1. To talk about ability
   e.g. I can take care of myself.

2. To talk about possibility and certainty
   e.g. The swimming pool might close due to the bad weather.

3. To talk about necessity and obligation
   e.g. You mustn’t use mobile phone at school.

4. To give advice
   e.g. You should have a balanced diet.

The form of modal verb:

• We keep the base verb after the modal verb:

Subject	modal verb	base verb
I	can	read	French.
	cannot (can’t)	see	the picture.
You	need to	tell	the truth.
	do not need to (don’t need to)	wear	a helmet.
The children	should	do	their homework.
	should not (shouldn’t)	run	fast.
We	have to	arrive	on time.
	do not have to (don’t have to)	read	the books.

Exercise:

You _______________ (must / can) keep quiet in the library. Otherwise, you will be forced to leave.

You _______________(may / should) do more exercise to reduce the weight. It is the doctor’s advice.

Students _______________(can / need to) hand in their homework on time. Otherwise, they will be punished.

I _______________(can / might) speak three languages.

The post office _______________(need to / may) close early because it is a public holiday.

I _______________(can / ought to) call my parents because I will come home late.

1. You must keep quiet in the library. Otherwise, you will be forced to leave.
2. You should do more exercise to reduce your weight. It is the doctor’s advise.
3. Students need to hand in their homework on time. Otherwise, they will be punished.
4. I can speak three languages.
5. The post office may close early because it is a public holiday.
6. I ought to call my parents because I will come home late.