Mastering Modal Verbs: Unlocking the Full Potential of ‘Can,’ ‘Should,’ ‘Must,’ and More

 

If the English language were a bustling metropolis, its verbs would be the workers, endlessly toiling away to keep everything moving—building sentences, driving meaning, and providing structure. Among them, however, a peculiar class of workers stands out. They do not bend to the same rules as their colleagues, nor do they clock in and out in predictable ways. These are the modal verbs, the free-spirited bohemians of grammar. They come in a small, tight-knit gang—can, could, should, would, may, might, must, shall, will—and like any good gang, they have their quirks, their mysteries, and their indispensable skills.

To many learners of English, modal verbs seem less like a team of linguistic helpers and more like tricksters. Why does can not come with an -s for third person singular, when every other respectable verb dutifully dons its -s for he, she, or it? Why can’t one say to must or to can? And why is it that these small words, seemingly so modest, carry the power to alter entire worlds of meaning? A mere shift from should to must changes polite advice into a stern command; swap may for might and suddenly possibility seems far less likely. For all their brevity, modals wield disproportionate influence.

Take can, for example. It is a little word with big muscles. It expresses ability: I can swim, which is both factual and reassuring if you are being pushed into the pool. It expresses permission: You can leave early, which to a weary employee sounds like freedom itself. It also deals in possibility: Accidents can happen, the sombre reminder printed on safety posters. Yet, with all its uses, can stubbornly resists the normal trappings of verbs. It does not conjugate, it does not bow to infinitives, and it certainly does not suffer fools who attempt to say to can.

Its cousin could adds an extra layer of slipperiness. It looks like the polite, hypothetical elder sibling of can. Could you pass the salt? is softer, gentler, and much less likely to provoke glares across the dinner table than the blunt Can you pass the salt? One is a question of ability; the other, a request in disguise. Could also ventures into the realm of possibility: It could rain later. The speaker here is not delivering a forecast so much as a philosophical shrug. One could almost hear the clouds giggling at the vagueness.

Then comes must, the bossy one. While can is versatile and could is coy, must brooks no nonsense. You must wear a helmet. No wiggle room, no excuses. Yet even here, the English language cannot resist introducing nuance. You must be tired does not command, but instead deduces, as if Sherlock Holmes had quietly wandered into the grammar lesson. One word, two entirely different shades of meaning—necessity and logical conclusion—delivered without ceremony.

Should is the moral philosopher of the group, always weighing in with advice. You should eat more vegetables sounds helpful, though inevitably delivered when one’s plate is already piled high with chips. It operates in the hazy territory between suggestion and obligation, a sort of halfway house where duties go to negotiate. If must is the sergeant-major, should is the earnest guidance counsellor, trying to make everyone better people without quite insisting on it.

And then we have may and might, the pair of hesitant fortune-tellers. You may take the exam again grants permission; It may snow tomorrow predicts possibility. Might simply dials down the certainty a notch, hovering in the realm of the probable-but-doubtful. It is the difference between You may win the lottery (unlikely, but mathematically possible) and You might win the lottery (utterly fantastical, though one continues to buy tickets). Learners often struggle with the subtle distinctions here, but perhaps that is the point: English speakers themselves often use them interchangeably, as if hedging bets is the default national pastime.

If modals are quirky in meaning, they are even stranger in form. They do not add -s for third person singular. They do not require do in questions (Can you swim? not Do you can swim?). They lack infinitives and participles, meaning there is no to must or musted. One cannot be canning or have shoulded. These omissions make them simultaneously easier and harder: easier because there are fewer forms to memorise, harder because they break every other pattern learners have painstakingly internalised. They are like the eccentric uncles at a family gathering—unpredictable, but essential for making the party interesting.

For teachers, modal verbs often present an opportunity to indulge in performance. Consider a classroom exercise in which students rank statements by strength of obligation: You must finish your homework; You should finish your homework; You could finish your homework. Delivered in escalating tones of authority—from authoritarian bark to gentle suggestion—it becomes clear that modals are not just words but instruments of social interaction. They are about how one positions oneself in relation to others: commanding, advising, permitting, warning, hypothesising. To master them is not merely to master grammar, but to understand the subtle dance of human communication.

In everyday life, we see modals everywhere, often where we least expect them. On public transport signs: You must wear a face covering. In legal disclaimers: Liability may arise if…. In motivational posters: You can achieve anything. In the quiet panic of a friend realising they forgot their passport: I should have checked my bag. They function like linguistic mood lighting—casting shades of possibility, certainty, duty, or advice, without ever raising their voice.

Learners, however, often try to tame modals into logic. They ask: what is the precise difference between may and might? When should I use should instead of must? Teachers, equally, are tempted to answer with rules. Yet modals are less about rules and more about shades of meaning, intent, and tone. They exist not to provide mechanical precision but to help us navigate the soft edges of human interaction. A modal verb is as much about what you want to convey as about what you actually mean.

One might say that mastering modals is a little like learning to drive in central London. The rules exist, certainly, but much depends on interpretation, timing, and tact. Knowing when to press the accelerator of must and when to glide on the cautious handbrake of might is the true art. And like any art, it takes practice, mistakes, and the occasional traffic jam.

In the end, modal verbs are not a nuisance but a gift. They allow us to speak not just about what is, but about what could be, what should be, what must be, and what might never be at all. They are the little engines of nuance that make English such a rich, maddening, endlessly fascinating language. To study them is to realise that communication is not simply about transmitting facts; it is about negotiating relationships, obligations, and possibilities.

So the next time you hear a student say I must to study or She cans sing, smile gently. Remind them that these tiny words are eccentric for a reason. They bend the rules because they bend reality. And if, in the process, they cause confusion, well—that too might be their point. After all, what is English without a little mystery?

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