must

1. health and safety

2. you must wear a helmet

3. you must wear gloves

4. you must wear a mask

5. you must wear boots

6. you must wear safety glasses

7. sub+mustn´t+infinitive

8. sub+must+infinitive

9. its necessary to do something

10. example

11. students must pass an entrance examination to study at this school

12. mary you must not pay in the street

13. this must be the rigth address