Must and Have to

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Must and Have to

Must	Strong necessity for present or future; Everyone must be back here by 6 o’clock.
Mustn’t	Prohibition – the speaker himself forbids; You mustn’t do that again.
Have to	Necessity – the speaker is not ordering or openly supporting an order (as with must).  He is simply stating a fact; You will have to wait for three hours at Rome Airport. You don’t have to fill up the forms – simply inform the section. (it is not necessary)
Had to	It is used for the necessity in the past; I had to pay $5 to get in! I showed my student’s card, and didn’t have to pay to get in.