1must be\ must do 用于现在时
He keeps looking at you, he must like you.
She looks so beautiful, she must be a model.
He has been working out for 5 years, he must be very strong.
2must have been\ must have done用于过去时
He didn't show up last week, he must have been on vacation.
She must have been very excited, when her boyfriend proposed to her last night.
You got a 20% pay rise, you must have done a great job.
You must wear a suit when you have a interview.
He must finish all his work before the meeting.
We must double confirm it before release.
You must fasten your seatbelt when you're driving.
You must show your passport to the immigration officer.
You must follow the rules.
You must see a doctor, you've been sick for a week.
You must read that book! It's amazing!
You must come to our party tonight! It'll be so much fun!
Why must she always interrupt me?
Why must you argue with each other everyday?
Why must you make so much noise?
You may think the insurance is unnecessary, but it's a must.
Eating Roast duck is a must if you come to Beijing.
It's a must to try different kinds of beer in Germany.