Must vs. Have to

Sometimes we can use must or have to to mean the same thing.
Example:
I need to be at the airport in one hour, so I must / have to go.

Generally, we use must for expressing personal feelings, and have to for expressing facts.

Example:
That new restaurant is great! You must go there!
You have to turn off your mobile phone in a museum.

We use must for the present or future, but not the past. We can use have to for all tenses (i.e., change have to to had to).

For negative statements and questions, we generally use do / does / did with have to.

Example:
You don't have to participate in the phone conference. CORRECT
You have not to participate in the phone conference. INCORRECT

Why did you have to tell the boss what I said? CORRECT
Why had you to tell the boss what I said? INCORRECT

Must not / mustn't and don't have to have different meanings. Must not / mustn't means it is forbidden. Don't have to means it is not necessary.

Example:
You mustn't do personal work on the company's computers.
You don't have to attend the meeting if you don't want to.

I _____ remember to thank him for his help on the project.
1. have to
2. had to
3. must
4. mustn't
You _____ interrupt him while he's in a meeting.
1. don't have to
2. mustn't
3. must not
Yesterday was a holiday, so I _____ go to work.
1. mustn't
2. don't have to
3. didn't have to
4. did not have to
We _____ check in two hours before our flight.
1. must
2. had to
3. have to
Why did he _____ work on Sunday?
1. must
2. had to
3. have to
She _____ wear glasses when using her computer.
1. must
2. has to
3. must to
4. had to
5. didn't have to
6. doesn't have to
7. did not have to
8. does not have to
We're on flex time, so we _____ start work at any particular time.
1. mustn't
2. don't have to
3. do not have to
The company parking lot was full this morning, so I _____ park on the street.
1. must
2. have to
3. had to
The meeting was cancelled, so he _____ go to Berlin next week.
1. mustn't
2. has to
3. doesn't have to
4. does not have to
Have you ever _____ make a presentation in English?
1. had to
2. must
3. will have to
I _____ stop at the store after I finish work today to pick up a few groceries.
1. must
2. had to
3. have to
She _____ go to work today until noon because she worked late last night.
1. mustn't
2. has to
3. doesn't have to
4. does not have to
5. didn't have to
6. did not have to