Must

Have to

‘Must’ is personal. We use ‘must’ when we give our personal feelings
She is a real nice person. You must meet her.

 

‘Have to’ is impersonal. We use ‘have to’ for facts, not for our personal feelings.
You have to do something because of a rule or the situation: You can’t turn left here. You have to turn right.
 

We use ‘must’ to talk about the present and future, but not the past.
We must go now.
We must go tomorrow.
 

We use ‘Have to’ in all forms.
I had to go to hospital.
Have you ever had to go to hospital?
I might have to go to hospital.
 

‘Mustn’t’ and ‘don’t have to’ are completely different.
You mustn’t do something = it is necessary that you don’t do it.
You don’t have to do something = You don’t need to do it (but you can if you want )
 

In questions and negative sentences with ‘have to’, we normally use do/does/ and did :
What do I have to do to get a driving license?
Why did you have to go to hospital?