1. The Role of “Must” for Obligation

• “Must” is a modal verb used to express strong necessity or obligation. When we use “must,” it often implies that the speaker feels strongly about the requirement or sees it as important, urgent, or necessary.

2. Usage of “Must”

a. Expressing Personal Obligation

“Must” is often used to express a strong internal or personal obligation. It reflects a speaker’s view or sense of duty.

• Example:
  “I must finish my homework before going out.”
  (The speaker feels a strong need or duty to complete the homework.)

b. Rules and Regulations

“Must” is commonly used to state rules, regulations, or strong guidelines.

• Example:
  “Visitors must wear masks in the museum.”
  (A rule or regulation is being highlighted.)

c. Giving Advice or Warnings

“Must” can also be used when giving advice, particularly when it carries a sense of urgency or seriousness.

• Example:
  “You must see a doctor if your symptoms persist.”
  (This indicates a strong recommendation, almost like an obligation.)

3. Difference Between “Must” and “Have to”

While “must” and “have to” both express obligation, there are subtle differences:

• “Must” typically implies an internal obligation, often influenced by the speaker’s judgment or feelings.
  Example: “I must call my friend today.” (The speaker feels personally compelled.)
• “Have to” indicates an external obligation, often due to external factors, rules, or circumstances.
  Example: “I have to call my friend because it’s his birthday.” (This is more about an external reason.)

4. Negative Form: “Must Not” (Prohibition)

When “must” is used in the negative form, “must not” (or “mustn’t”), it indicates prohibition.

• Example:
  “You must not smoke inside the building.”
  (This strongly prohibits smoking within the building.)

5. Practice Time! 🎉

Fill in the blanks with the correct form of “must” or “must not”:

1. You _______ bring your ID to enter the premises.
2. She _______ leave now if she wants to catch the train.
3. Visitors _______ take photos inside the art gallery.
4. I _______ remember to call my grandmother tonight.

✅ Answers:

1. must
2. must
3. must not
4. must