How do you express rules, give strong advice, or talk about what’s necessary? The modal verbs “must,” “should,” and “have to” are your essential tools for giving clear guidance and recommendations to others. Understanding the small differences between them will make your English much more precise.🚦
Function & Usage
These words all express obligation or advice, but with different levels of strength and meaning.
- Must (Strong Obligation / Rule): Used for very strong obligations, rules, or something the speaker feels is essential.
Example: You must wear a helmet when riding a motorcycle. (It’s a law). - Have to (Strong Obligation / External Rule): Very similar to ‘must’, but often used for obligations that come from an outside source (a boss, a rule, a situation).
Example: I have to work on Saturday. (My boss told me). - Should (Advice / Suggestion): Used to give advice or say what you think is a good idea. It is not a strong obligation.
Example: You look tired. You should get some rest.
The Structure (Form)
Both ‘must’ and ‘should’ are simple modal verbs that never change. ‘Have to’ is slightly different, as it changes for the subject.
| Modal | Structure | Example |
|---|---|---|
| Must / Should | Subject + must/should + Base Verb | You should go. / He must leave. |
| Have to | I/You/We/They + have to + Base Verb He/She/It + has to + Base Verb |
We have to study. She has to work. |
Important Note on Negatives:
Mustn’t means something is prohibited (Don’t do it!). Example: You mustn’t smoke here.
Don’t have to means there is no obligation (It’s not necessary). Example: You don’t have to come if you’re busy.
Common Mistakes to Avoid
- Using “to” after must/should: Incorrect: “You must to be quiet.” Correct: “You must be quiet.”
- Confusing “mustn’t” and “don’t have to”: This is a very important difference. “You mustn’t pay” is a prohibition. “You don’t have to pay” means it’s free!
Let’s see it in action! 🎬
Doctor: You look unwell. You should see a specialist.
Patient: Okay, I will. What else?
Doctor: You must stop smoking immediately. It’s essential for your health.
Friend 1: I’m so busy tomorrow.
Friend 2: You don’t have to come to the party if you’re tired. It’s okay!
Friend 1: Thanks, but I really want to come. I think I should finish my work tonight instead.
New Employee: What are the rules here?
Manager: Well, you have to be at your desk by 9 AM. And you mustn’t use your phone for personal calls.
Check Your Understanding! ✅
1. (Advice) You look sick. You go home.
2. (A rule) In a library, you be quiet.
3. (External obligation) She wear a uniform to school.
4. (Prohibition) You touch the art in the museum.
5. (No obligation) It’s Sunday tomorrow, so I wake up early.
6. That’s a great movie. You ___ see it!
7. To get a driver’s license, you ___ pass a test.
8. You ___ talk on the phone while you are driving. It’s dangerous and illegal.
9. The museum is free. You ___ pay.
10. I think we ___ invite Sarah to the party.
