Study the information about ‘a scale of choice’ and expressing necessity in other tenses.
1. We use should and ought to when it’s advisable, but there is some choice.
You should go to the doctor.
2. Had better is stronger, it is a warning.
You’d better have medical check.
3. Have to, have got to (less formal) and must (when you have no choice).
You have to/have got to/must take medicine.
4. We tend to refer must when we refer to ourselves, with you to express urgency, in public notices, pressing invitations or advice.
I really must weed this garden.
You must come and repair that fence.
5. Must can refer to present or the future.
He must speak to me tomorrow.
6. Had is used to show that we couldn’t avoid doing something.
I had to leave at 5.
Should have shows we’ve failed to do something.
I should have left at 8.30.