IELTS grammar: Modal Verbs

Modal verbs matter for scoring because they let a writer or speaker signal exactly how confident, tentative, or obligated they are about a claim, and IELTS specifically rewards this kind of calibrated hedging in higher-band Task 2 essays and Part 3 answers, where blunt, absolute claims are treated as less sophisticated than carefully graded ones. The recurring error at Band 5-6 is not using the wrong modal in a way that produces ungrammatical sentences, but using too narrow a range of modals — usually just "will," "can," and "should" — repeated throughout an essay regardless of how confident or tentative the underlying claim actually is, which reads as underdeveloped nuance rather than a grammar mistake as such.

For expressing degrees of certainty about a future or general claim, English offers a genuine gradient, and matching the modal to your actual confidence level is the core skill: "This will definitely happen" (near-certain, strong claim), "This is likely to happen" or "This may happen" (probable but not certain), "This might happen" or "This could happen" (possible, less likely), and "This is unlikely to happen" (probable in the negative direction). INCORRECT, in the sense of being imprecise rather than ungrammatical: "Technology will solve this problem" stated as a flat prediction the essay cannot actually support. MORE PRECISE: "Technology may help address this problem, though it is unlikely to solve it entirely without matching changes in policy." The second version is not just more hedged, it is more defensible, since Task 2 essays are frequently marked down not for grammar alone but for overclaiming certainty the argument hasn't earned.

For obligation and recommendation, "must" is grammatically strong and implies a firm, near-legal requirement, which makes it often too forceful for Task 2 essay recommendations about policy or social behaviour: "Governments must invest in public transport" reads as an unqualified demand, whereas "should" is the more natural, appropriately hedged choice for a policy suggestion the essay is arguing for rather than asserting as an already-settled requirement: "Governments should invest in public transport." "Have to" sits closer to "must" in force and is used for external, often circumstantial obligation rather than a moral or policy recommendation: "Commuters have to change trains twice on this route" describes an external fact, not a recommendation, and using it in place of "should" for an essay's own argument would sound oddly detached from the writer's actual stance.

A common error is overusing "can" to mean "sometimes happens" or "is theoretically possible," which produces claims so broad they carry almost no argumentative weight: "Technology can cause problems" is technically true but nearly meaningless, since almost anything "can" cause some problem under some circumstance. INCORRECT, as a supporting sentence in an argument: "Social media can affect mental health, so it can be a concern." CORRECT, more specific and more defensible: "Social media often affects mental health negatively among teenagers specifically, which is why it has become a genuine policy concern." Replacing a vague "can" claim with either a more precise modal ("often," "tends to," "is likely to") or an explicit qualifier narrows the claim to something the essay can actually support with reasoning.