Mastering Modal Verbs: Must and Mustn't (Obligation)

Welcome to your guide on modal verbs, specifically focusing on must and mustn't. Understanding these verbs is essential for expressing obligation in English. Whether you're a beginner or just brushing up on your skills, this article will help you grasp the rules and usage of these important modal verbs.

What are Modal Verbs?

Modal verbs are auxiliary verbs that express necessity, ability, permission, or possibility. In this article, we will focus on must and mustn't, which indicate obligation and prohibition.

Using Must

Must is used to express a strong obligation or necessity. When you say you must do something, it means you have to do it.

Using Mustn't

Mustn't is used to indicate something that is prohibited or not allowed. When you say you mustn't do something, it means you should not do it.

Rules Summary

Modal Verb	Usage	Example
Must	Expresses obligation	You must finish your homework.
Mustn't	Expresses prohibition	You mustn't smoke here.

Examples of Must and Mustn't

Here are some examples to illustrate the correct and incorrect usage of must and mustn't:

✅ You must wear a seatbelt.
❌ You mustn't wear a seatbelt.
✅ Students must submit their assignments on time.
❌ Students must submit their assignments late.
✅ You must turn off your phone in class.
❌ You must turn on your phone in class.
✅ We must help each other.
❌ We mustn't help each other.
✅ You must drink water every day.
❌ You mustn't drink water every day.
✅ You must follow the rules.
❌ You mustn't follow the rules.
✅ She must study for the exam.
❌ She mustn't study for the exam.
✅ You must respect your elders.
❌ You mustn't respect your elders.
✅ We must arrive on time.
❌ We mustn't arrive on time.
✅ You must keep the environment clean.
❌ You mustn't keep the environment clean.

Pro Tip: Remember that must is for things you have to do, while mustn't is for things you cannot do. Keep practicing with these examples!

Common Mistakes

One common mistake is confusing must with have to. While they are similar, must is often used for personal obligations, while have to can refer to external obligations.

Conclusion

Understanding modal verbs like must and mustn't is crucial for expressing obligation and prohibition in English. With practice, you will become more confident in using these verbs correctly. Keep exploring and practicing your English grammar skills!