I must do my homework.
You mustn’t be late for class.
We must wear our school uniform.
We can use ‘must’ to talk about rules. For the negative, we can say ‘must not’ or ‘mustn’t’.
Parents must take care of their children.
You mustn’t shout in the library.
She must not forget her books.
The main verb is without ‘to’.
He must be careful when cutting food.
I mustn’t make a mess.
We say... We don’t say...
You must look both ways when crossing the road. (NOT You must to look both ways when crossing the road.)
We mustn’t run in school. (NOT We mustn’t to run in school.)
Children must respect their parents. (NOT Children must respecting their parents.)