Student or Learner
When thinking of "must", "don't have to", "must not", many grammar books say the opposite of "must" is "don't have to", not "must not". "must not" is just a negative obligation. But it's kind of confusing even though I know "must not" is a parallel obligation with "must", but also seems the opposite of "must" considering the degree of obligation. I don't know how to tell the three. Which is which's opposite?
ex1)You must go <=> You don't have to go
You must not go
You must go / You have to go - There is a positive obligation to go.
You must not go - There is a positive obligation to not-go.
You don't have to go / you needn't go - There is no obligation to go (but you can if you want to).
You may go (formal) - You have permission to go.
You may not go (formal) You are not permitted to go. You are forbidden to go.