The word “must” is versatile and essential in English for expressing necessity, obligation, strong recommendations, and more. In this guide, we’ll explore the various ways to use “must” effectively, provide examples, identify common mistakes, and offer practice exercises.
1. To Express Strong Necessity or Obligation
“Must” is often used to indicate that something is required or compulsory. It expresses a strong sense of necessity.
Examples:
- Positive: “You must wear a helmet while riding a motorcycle.”
- Negative: “You must not smoke in public areas.”
Common Mistake: Using “have to” instead of “must” in formal settings where “must” shows urgency.
- Incorrect: “You have to attend the meeting.” (Less formal)
- Correct: “You must attend the meeting.”
2. To Show Deduction or Logical Assumption
“Must” is also used to make an assumption or deduction about something that we believe is likely true based on evidence or logic.
Examples:
- “The lights are off, so they must have gone to sleep.”
- “You’ve been working all day. You must be tired.”
Common Mistake: Confusing “must” with “might” or “could,” which indicate lower certainty.
- Incorrect: “He might be home by now.” (Lacks strong assumption)
- Correct: “He must be home by now.”
3. To Express Strong Advice or Recommendation
“Must” can provide a strong recommendation or advice, similar to saying, “It’s very important.”
Examples:
- “You must try the new Italian restaurant!”
- “If you visit Paris, you must see the Eiffel Tower.”
Common Mistake: Using “should” when you want to emphasize something as essential.
- Incorrect: “You should see a doctor.”
- Correct: “You must see a doctor.”
4. To Indicate a Prohibition (Negative Form)
“Must not” or “mustn’t” is used to prohibit or strongly advise against an action.
Examples:
- “You must not drive if you feel dizzy.”
- “Visitors mustn’t touch the artwork in the gallery.”
Common Mistake: Misusing “can’t” in place of “mustn’t,” which can change the level of prohibition.
- Incorrect: “You can’t eat here.”
- Correct: “You mustn’t eat here.”
5. To State Rules or Laws
“Must” is commonly used to state rules, regulations, or laws.
Examples:
- “All passengers must fasten their seatbelts.”
- “You must wear a mask in the hospital.”
Common Mistake: Replacing “must” with “should,” which weakens the statement and makes it less formal.
- Incorrect: “You should wear a mask in the hospital.”
- Correct: “You must wear a mask in the hospital.”
6. To Emphasize a Strong Desire or Personal Determination
“Must” is sometimes used to express a strong personal determination or desire to do something.
Examples:
- “I must finish this book tonight!”
- “We must win this match.”
Common Mistake: Using “have to” instead of “must,” which weakens the expression of personal determination.
- Incorrect: “I have to finish this book tonight.”
- Correct: “I must finish this book tonight.”
7. For Hypothetical Situations or Future Plans (Less Common)
Although rare, “must” can be used in hypothetical or future situations to convey certainty or a strong intention.
Examples:
- “We must remember to bring sunscreen for the beach tomorrow.”
- “She must complete the report before the weekend.”
Common Mistake: Replacing “must” with “should,” making the future plan sound less urgent.
- Incorrect: “We should remember to bring sunscreen.”
- Correct: “We must remember to bring sunscreen.”
8. To Indicate Expectations or Requirements in Specific Situations
“Must” is often used to outline expectations or requirements for tasks, exams, or procedures.
Examples:
- “All students must submit their projects by Friday.”
- “You must complete all sections of the application form.”
Common Mistake: Using “need to” instead of “must” when the intention is to set a strict requirement.
- Incorrect: “Students need to submit their projects by Friday.”
- Correct: “All students must submit their projects by Friday.”
9. For Urgency in Directions or Instructions
“Must” is helpful in conveying urgent instructions, especially in emergencies or critical situations.
Examples:
- “You must leave the building immediately if you hear the fire alarm.”
- “Staff must follow safety protocols at all times.”
Common Mistake: Replacing “must” with “have to” in critical directions, which sounds less immediate.
- Incorrect: “You have to leave the building.”
- Correct: “You must leave the building.”
10. To Make Emphatic Requests or Suggestions
“Must” is also used for making emphatic requests or suggestions in a way that shows strong encouragement.
Examples:
- “You must come to our party!”
- “You must see this movie; it’s fantastic.”
Common Mistake: Using “ought to” instead of “must” when emphasizing a strong suggestion or request.
- Incorrect: “You ought to come to our party.”
- Correct: “You must come to our party!”
Common Mistakes to Avoid When Using “Must”
- Replacing “must” with “have to” in formal contexts – “Must” often sounds stronger and more formal.
- Using “must” for past actions – Use “had to” for necessity in the past.
- Incorrect: “I must go to the doctor yesterday.”
- Correct: “I had to go to the doctor yesterday.”
- Confusing “must” with “should” – “Must” shows strong obligation, while “should” is more like advice.
Exercise: Practice Using “Must” in Sentences
Fill in the blanks with the correct form of “must.”
- You ________ (must) submit your assignment by tomorrow.
- She ________ (must not) reveal confidential information.
- We ________ (must) try that new restaurant this weekend!
- You ________ (must) wear a uniform in the workplace.
- They ________ (must) be exhausted after such a long flight.