1. must and have to
Use must and have to to say that something is necessary.
You’ll be leaving college soon. You must think about your future.
We’re very busy at the office. I have to work on Saturday morning.
Mark has to get the car repaired. There’s something wrong with the brakes.

2. When we use the past, or the future with will, we need a form of have to.
Emma had to go to the dentist yesterday.
That wasn’t very good. We’ll have to do better next time.
And also in other structures, for example:
I don’t want to have to wait in the queue.
Emma has a toothache, she might have to go to the dentist.
Mark has had to drive all the way to Rome.

3. must or have to? Both express necessity but are used differently:
We use must when the speaker feels that something is necessary:
The doctor to his patient: “You must exercise,”
“We must be quiet, the children are sleeping.”
To express a wish or strong desire:
I must buy a newspaper; I want to see who won last night.
We must invite Charles. We haven’t seen him in ages.

4. must or have to? Both express necessity but are used differently:
We use have to when the situation makes something necessary.
I have to exercise. (The doctor told me to.)
We have to be quiet. (The teacher told us to.)
I have to buy another news paper; the first one got wet.
We have to invite Charles; he invited us last time.

5. mustn’t and don’t have to
We use mustn’t to say that something is a bad idea:
You mustn’t wash those glasses in the dishwasher; they’ll be ruined.
I mustn’t forget my keys again.
You mustn’t be late for the meeting.

6. mustn’t and don’t have to
We use don’t have to when something is not necessary
You don’t have to wash those glasses; they’re clean.
She doesn’t have to finish the translation today; she can do it over the weekend.

7. need and needn’t
Need can substitute must or have to when indicating that something is necessary.
Must we leave early? / Do we have to leave early? / Do we need to leave early?
In the negative needn’t or don’t need to is used with the same meaning as don’t have to.
You needn’t come to the meeting tomorrow. / You don’t need to come to the meeting tomorrow. You don’t have to come to the meeting tomorrow.

8. should and ought to
Use should and ought to to say what is the best thing or the right thing to do.
You’re not very well. Perhaps you should see a doctor.
Your father was very kind to me. I ought to buy him a gift.
People shouldn’t / ought not to break promises.
Where should I put this picture do you think?

9. Complete with the correct form: must, have to, or should/ought to
You ____ tell anybody. It’s a secret.
It’s Sunday so I ____ go to work.
That skirt is perfect for you. I think you ____ buy it.
We ____ wear a uniform at out school. I hate it.
I ____ remember to give you back the money I borrowed.
You ____ eat so much white bread. It’s not very good for you.
Peter bought the cinema tickets and dinner last night. I ____ pay for anything.
Our car broke down on holiday so we ____ rent a car for a week.

10. drive slowly in the fast lane stop at traffic lights
Imagine you are going on a long car journey. In pairs make true sentences about Italy. Use you have to, you should, you don’t have to, you shouldn’t, you mustn’t.
check your car oil
drive slowly in the fast lane
stop at traffic lights
stop and rest every two hours
wear a seat-belt in the front
clean you car
go over the speed limit
use a mobile phone while you’re driving
let children sit in the front
wear a seat-belt in the back

11. possibility and certainty: may, might, could, must
David: Whose bag is that? Doris: I don’t know. It may belong to Maria’s friend. David: It might be a bomb. It could explode at any moment! Daniel may not / might not get the job. She isn’t answering the phone. She must be out. You haven’t walked very far. You can’t be tired already!