We say something is a must when it is required that we do it. In other words, we have to follow the rules otherwise we won't get what we need. For example, we can say that getting a driver's license is a must if you want to drive, or taking the TOEFL is a must to enter most U.S. universities.
A: Do we have to do a project for this class? I don't know if I'll have time to do one this semester. I have such a busy schedule.
B: Yeah, unfortunately. The professor said it's a must in order to pass the course.
A: Great! I have about 5 huge papers to write, this project, and I have to design a Web page for a small company. Plus, I have to keep working. It's going to be a busy semester.
B: You get to design a Web page? That's awesome!
A: Yeah. That's also a must. I'm going to enjoy doing it. I just wish I didn't have to do it this semester.
B: Well, good luck. I'm sure you'll be able to do it. You always do.
A: Thanks. I hope so, too.
Alright folks, think of a few things that are requirements for you right now: your exams in school, saving money for rent, getting a visa, finding a job, etc. Make sentences about why they are a must, and say them out loud for practice.