1. have to x must
by Petra Halfarová

2. Compare: I have to get up early tomorrow. School starts at 7 am.
I must get up early tomorrow. I want to study before the test.
I have to go to visit my grandma on Sunday. My parents told me to.
I must visit my grandma soon. I haven’t seen her for ages!
I have to be nice to my little brother.
I must be nice to my girlfriend!

3. Must speaker agrees (his feeling) I must wash my hair tonight!
I can feel my hair is dirty and I want to do something about that.
You must come for a visit at the weekend!
I really want you to come.
I must go to bed earlier tonight.
I’ve got some personal reason for it.

4. Must we are very sure that something is true
There’s no heating on. You must be freezing.
I really think you are feeling very cold.
It must be nice to live in Italy.
I really think so.
You must tell me all about your new boyfriend.
I really want to know about your boyfriend.

5. Must very strong obligations (rules, laws, warnings…)
You must have your passport with you when you want to visit the USA.
It’s the law.
You must change your shoes from 11 November to 31 March.
One of the school rules.
You must have a driving licence if you want to drive a car.

6. Have to something / somebody else tells me to do something
I have to work late tomorrow.
My boss told me so.
I have to wash the car at the weekend.
My parents told me so.
You have to pay $ 30 to see the band.
That’s the price of a ticket.

7. If you are not sure… use HAVE TO it’s not that strong
it’s more used in spoken language
Google search results:
must:  000 000 
have to:   25 270 000 000

8. Grammar difference Must only in PRESENT (with future reference)
in PAST = HAD TO
In FUTURE = WILL HAVE TO
I had to study hard to become a lawyer.
I musted study hard to become a lawyer.
I will have to study much harder if I want to past the final exam.
I will must study much harder if I want to past the final exam.

9. MUSTN’T X DON’T HAVE TO You mustn’t smoke here!
It’s not allowed to smoke here.
You mustn’t use the internet during a test.
It’s prohibited to use the internet during a test.
We don’t have to wear a uniform at school.
We can wear whatever we want at school.
Children under 5 don’t have to pay the entrance fee.
You will pay no money for children under 5 to enter.