Modal verbs.Must

Use must when you think it is necessary or very important.The windows are dirty I must clean them.We must go to the bank today.We have not got any money.I must hurry.I must not be late.Needn't

I needn't do it-it is necessary to do.I needn't clean the window.They aren't dirty.Should It is a good thing to do or the right thing to do.It is a good film.You should go and see.Have to-it is necessary for me to do it.I'm obliged to do it.Past-Had to.Question and negative do does did.

Tom doesnt have to workvery hard.He has got an easy job.Have to-When you are not giving your personal opinion.

Jill will not be here this afternoon,She has to go to the doctor.In many countries men have to do military service.(this is not my opinion- it is the law in those countries)