Parts of Speech Intermediate

Modal Verbs

Master English modal verbs: ability, permission, possibility, obligation, advice and deduction. Learn the differences between similar modals and how to use them correctly in PTE and IELTS writing and speaking.

What is Modal Verbs?

Modal verbs (can, could, may, might, must, shall, should, will, would, ought to, need to, have to) add meaning about possibility, ability, permission, obligation, advice or deduction. They are followed by the base verb (infinitive without "to") and have no -s in the third person. Using modals accurately and with variety is a key differentiator between band 6 and band 7+ in IELTS Writing.

Rules & Formation

Modals are followed by base verb (infinitive without "to"): "She can speak three languages." NOT "She can speaks/to speak."
No -s for third person: "He must submit the form." NOT "He musts."
Ability: can (present), could (past), be able to (all tenses).
Permission: can/may (informal/formal). Request: could/might (more polite than can/may).
Possibility: may/might (uncertain), could (hypothetical), must/can't (logical deduction).
Obligation/Necessity: must (strong, internal), have to/need to (external), should/ought to (advice).

Examples

Students can access all practice materials online. (ability/permission)

This approach may lead to unintended consequences. (uncertain possibility — academic)

The government should invest more in public education. (advice/recommendation)

Applicants must submit all documents by the deadline. (strong obligation)

She could have scored higher if she had practised more. (past unreal possibility)

This must be the correct answer — the evidence is clear. (logical deduction)

🎯 Exam Tip — PTE & IELTS

In IELTS Writing Task 2, modals are essential for making recommendations ("governments should"), expressing uncertainty ("this may lead to"), and hedging claims ("could arguably"). Using "must" for obligations and "should" for recommendations shows control. In PTE Write Essay conclusions, "should" and "must" carry different weights — "must" is stronger and more direct; "should" is appropriate for recommendations.

Frequently Asked Questions

What is the difference between "must" and "have to"?

"Must" typically expresses an internal obligation, a rule the speaker imposes: "I must study harder" (I am telling myself). "Have to" expresses an external obligation, a rule imposed by someone/something else: "I have to show my passport at the border" (the rule exists externally). In academic writing, both are used for strong obligations, but "must" is more formal and more common in written recommendations.

What is the difference between "may", "might" and "could" for possibility?

"May" expresses a real, current possibility: "The results may be published this week." "Might" is slightly more uncertain: "Results might be delayed." "Could" expresses a theoretical or more distant possibility, often in conditionals: "This could be a significant finding if confirmed." In IELTS academic writing, "may" and "might" are used for hedging — expressing uncertainty rather than stating facts — which is an important academic register feature.

How do I use modals in the past?

Past modals use: modal + have + past participle. "She should have submitted earlier." (past advice — not followed). "He must have forgotten." (past deduction). "They could have arrived by now." (past possibility). "If she had prepared, she might have passed." (third conditional). These past modal forms demonstrate a sophisticated level of grammatical control and are expected at IELTS band 7+.

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