Modal Verbs: Essential Rules for CMAT Verbal Ability

2026-06-27

Introduction

Modal verbs are a crucial part of English grammar, adding nuance and specific meanings to main verbs. For the CMAT Verbal Ability section, understanding modal verbs is essential for questions related to sentence correction, fill-in-the-blanks, and error spotting. Mastering their usage will help you convey precise meanings and avoid common grammatical errors.

What Are Modal Verbs?

Modal verbs are a type of auxiliary (helping) verb that express modality, such as possibility, ability, permission, obligation, advice, and necessity. They always accompany a main verb in its base form (infinitive without 'to').

Common modal verbs include:

• can, could
• may, might
• will, would
• shall, should
• must
• ought to

Types and Functions of Modal Verbs

Modal verbs add specific meanings to the main verb. Here's a breakdown of their primary functions:

Ability

• Can: Expresses present ability or capability.
  • Example: She can speak three languages.
• Could: Expresses past ability; also used for polite requests.
  • Example: He could run fast when he was young.

Permission

• Can: Informal permission.
  • Example: You can leave now if you want.
• Could: More polite request for permission.
  • Example: Could I borrow your pen for a moment?
• May: Formal permission.
  • Example: You may enter the examination hall.

Possibility/Probability

• May/Might: Expresses possibility or uncertainty.
  • Example: It may rain tomorrow. (Slightly higher chance)
  • Example: She might come to the party. (Slightly lower chance)
• Could: Expresses a possibility, often hypothetical.
  • Example: The plan could work if we try harder.
• Can: Used for general possibility or characteristic.
  • Example: Accidents can happen to anyone.

Obligation/Necessity

• Must: Expresses strong obligation, necessity, or certainty.
  • Example: You must submit your assignment by Friday.
  • Example: He must be tired after working all day.
• Have to: Expresses external obligation or necessity (often imposed by rules or circumstances).
  • Example: We have to wear uniforms at school.
• Should/Ought to: Expresses advice, recommendation, or moral obligation.
  • Example: You should study harder for the exam.
  • Example: We ought to help those in need.

Advice/Suggestion

• Should: Gives advice or makes a suggestion.
  • Example: You should eat healthier.
• Ought to: Similar to 'should', often implying moral duty.
  • Example: Students ought to respect their teachers.

Prohibition

• Must not (Mustn't): Expresses strong prohibition.
  • Example: You must not use your phone during the exam.
• Cannot (Can't): Expresses inability or impossibility.
  • Example: You cannot smoke in here.

Requests and Offers

• Will/Would: Used for requests and offers.
  • Example: Will you please help me? (Less formal)
  • Example: Would you mind opening the window? (More polite)
• Can/Could: Also used for requests.
  • Example: Can you pass the salt?
  • Example: Could you please repeat that?

Key Rules for Using Modal Verbs

To use modal verbs correctly, remember these fundamental rules:

• Followed by Base Form: A modal verb is always followed by the base form (V1) of the main verb, without 'to'.
  • Correct: He can swim. (Not can to swim or can swims)
• No -s in Third Person Singular: Modal verbs do not take an '-s' for the third person singular (he, she, it) in the present tense.
  • Correct: She can sing. (Not she cans sing)
• No 'Do/Does' in Questions/Negatives: Do not use 'do' or 'does' with modal verbs for questions or negative statements.
  • Correct: Can you help me? (Not Do you can help me?)
  • Correct: He cannot come. (Not He does not can come)
• Cannot be Chained: You cannot use two modal verbs together.
  • Incorrect: He will can come.
  • Correct: He will be able to come.
• Question Formation: Form questions by inverting the modal verb and the subject.
  • Example: He should leave. -> Should he leave?

Commonly Confused Modals and Exam Traps

Understanding the subtle differences between similar modal verbs is crucial for CMAT.

Can vs. Could

• Can: Present ability, informal permission, general possibility.
• Could: Past ability, polite permission/request, specific possibility (often hypothetical).
  • Trap: Using 'can' for a past ability. Incorrect: I can swim well when I was young. Correct: I could swim well when I was young.

May vs. Might

• Both express possibility, but may suggests a slightly higher chance or formal permission, while might suggests a lower chance or is more hypothetical.
  • Example: It may rain. (50% chance)
  • Example: It might rain. (20% chance)

Must vs. Have to

• Must: Strong obligation, internal necessity, or firm conclusion/certainty.
  • Example: I must finish this project. (Self-imposed)
• Have to: External obligation, rule, or requirement.
  • Example: I have to wear a uniform for work. (Imposed by work)
  • Trap: Using 'must' for an obligation imposed by others in casual conversation; 'have to' is often more natural.

Should vs. Must

• Should: Advice or recommendation (softer obligation).
  • Example: You should consult a doctor.
• Must: Strong obligation or necessity (harder, more definitive).
  • Example: You must follow the doctor's advice.

Worked Examples for CMAT

Let's apply these rules to common CMAT-style questions.

Example 1: Fill in the Blank

You ______ pay your taxes by the deadline to avoid penalties.

a) should b) might c) must d) could

Answer: c) must. Paying taxes by the deadline is a strong obligation/necessity imposed by law.

Example 2: Error Spotting

Identify the error in the sentence: "She can to play the piano very well."

a) She b) can to play c) the piano d) very well

Answer: b) can to play. Modal verbs are followed by the base form of the verb without 'to'. The correct phrase is 'can play'.

Example 3: Sentence Correction

Which of the following sentences correctly expresses past ability?

a) I can climb trees when I was a child. b) I could climb trees when I was a child. c) I may climb trees when I was a child. d) I must climb trees when I was a child.

Answer: b) I could climb trees when I was a child. 'Could' is used for past ability.

Quick Revision & Exam Tips

• Base Form Rule: Always remember that modal verbs are followed by the base form of the main verb (V1) without 'to'. This is the most frequent error spot.
• Function Clarity: Identify what the sentence intends to express (ability, permission, obligation, etc.) to choose the correct modal.
• Politeness Levels: Differentiate between 'can' (informal), 'could' (polite), and 'may' (formal) for permission/requests.
• Context is Key: The context of the sentence will guide you in distinguishing between must (strong internal obligation/certainty) and have to (external obligation).
• No 's' or 'do/does': Modals don't change form for third person singular, nor do they use 'do/does' for negatives or questions.

Conclusion

Modal verbs are small words with significant impact on meaning. A solid grasp of their functions and rules will significantly boost your score in the Verbal Ability section of the CMAT exam. Pay close attention to the base form rule and the nuanced differences between similar modals. Practise these concepts with various exercises and past CMAT questions to lock the patterns in.