Must

Must= πρέπει / Mustn't= απαγορεύεται

You must eat three normal-sized meals a day.
You mustn't use mobile phones in class.

It's Sunday today. You don't have to wake up early.

​Don't have to= δεν χρειάζεται

John is a policeman. He has to wear a uniform at work.

Have to= πρέπει

Have to/ Don't have to

Should/ ought to

​Should/ ought to= καλό θα ήταν να

You are ill. You should stay in bed.
You are ill. You ought to stay in bed.

May/ Might

May/might= μπορεί

Mary isn't at home. She may/might be at school.