must
In the present tense, must takes the same form in all persons:
I must
you must
he/she/it must
we must
you must
they must
Must is followed by a base verb (infinitive without 'to').
I must eat more fruit. It's good for me.
You must go and see the new Will Smith movie. You'll love it!
We must remember to thank them for the lovely gift.
have to
In the present tense, have to takes the same form in all persons, but it becomes has to in the 3rd person:
I have to
you have to
he/she/it has to
we have to
you have to
they have to
Have to is followed by a base verb (infinitive without 'to').
I have to submit this assignment by 3pm tomorrow.
She has had three heart attacks, so now she has to have an operation.
You have to use the back door in the