1. HAVE, DON’T HAVE MUST, MUSTN’T
MODAL VERBS
HAVE, DON’T HAVE
MUST, MUSTN’T

2. CAN, CAN’T, WILL, WON’T, HAVE TO, MUST, SHOULD, WOULD LIKE TO, MIGHT…
What is a modal verb?
We use modal verbs to show if we believe something is certain, probable or possible (or not). We also use modals to do things like talking about ability, asking permission making requests and offers, and so on.
Modals are different from normal verbs: 1: They don't use an 's' for the third person singular. 2: They make questions by inversion ('she can go' becomes 'can she go?'). 3: They are followed directly by the infinitive of another verb (without 'to').
CAN, CAN’T, WILL, WON’T, HAVE TO, MUST, SHOULD, WOULD LIKE TO, MIGHT…

3. HAVE TO
We use HAVE TO + INFINITIVE to talk about RULES and OBLIGATIONS.
I have to get up at 7 everyday.
She has to speak English at work.
DO I have to get at 7 everyday?
DOES she have to speak English at work?
Note: WE CAN’T CONTRACT THE MODAL VERB HAVE TO
I have to work tomorrow. BUT NOT I’ve to work.

4. DON’T HAVE TO
We use DON’T HAVE TO + INFINITIVE to say that there is no obligation or that something is not necessary.
We dont’ have to wear a uniform to school.
She doesn’t have to work on Sundays.

5. MUST
We use MUST + INFINITIVE WITHOUT TO to talk about RULES and OBLIGATIONS.
I must study a lot for my English exam.
She must tidy her room before going out.

6. MUSTN’T
We use MUSTN’T (MUST NOT) + INFINITIVE WITHOUT TO to say something is prohibited.
You mustn’t leave your bags here.
You mustn’t smoke in the school.

7. Then, what’s the difference?
Must and have to are very similar, but there is a small difference.
We normally use HAVE TO for a general obligation (a rule at work, at school)
We normally use MUST for a personal obligation
(one that the speaker imposes)

8. Then, what’s the difference?
Mustn’t and don’t have to have completely different meanings.
You mustn’t go.  It’s forbidden. Don’t go.
You don’t have to go.  You can go if you want to, but it’s not necessary.
Impersonal YOU. We often use have to and must with impersonal you (people in general).
You have to wear a seatbelt in a car.
You mustn’t take photos in the museum.

9. YOU MUSTN’T ENTER
YOU MUSTN’T EAT OR DRINK

10. It is not necessary to bring the book. YOU DON’T HAVE TO BRING THEM
It is not necessary to bring the book. YOU DON’T HAVE TO BRING THEM. It is not necessary to clean the house today. YOU DON’T HAVE TO CLEAN THE HOUSE TODAY.