Don't park your car on bends. It is illegal. → You mustn't park your car on bends; it is illegal.

I want you to tidy the classroom. → You must tidy the classroom.

I need your help. It's too much work for me. → You must help me; it's too much work for me.

Promise that you'll never ever do it again! → You mustn't ever do it again!

It is important for me to pass the exam. → You must pass the exam.

It is against the law to drive without a seat belt. → You mustn't drive without a seat belt; it is against the law.

It's important not to blow your nose in public in Japan. → You mustn't blow your nose in public in Japan.

In the UK, it's important not to talk with your mouth full. → In the UK, you mustn't talk with your mouth full.

In some Muslim countries, it's important not to eat with your left hand. → In some Muslim countries, you mustn't eat with your left hand.

In lots of countries, it's important that you eat everything on your plate. → In lots of countries, you must eat everything on your plate.