What Are Modal Verbs & How to Use Them
Table of Contents
What Are Modal Verbs?
Modal verbs are a group of auxiliary verbs (sometimes in the classroom I may call them helping verbs for simplicity) that work with a main verb to show the speaker’s attitude or approach toward an action. They are called “modal” because they express modality, which refers to different ways of viewing or interpreting the action. These “modes” can involve possibility, ability, necessity, permission, likelihood, or assumption. In other words, modal verbs do not describe the action itself but add a layer of meaning about how certain, necessary, allowed, or possible the action is. For example, “She goes” states a fact, “She might go” suggests uncertainty, and “She must go” expresses obligation. The action “go” stays the same, but the modal changes the way we understand it.
Common modal verbs in English include can, could, may, might, shall, should, will, would, and must. The verb that comes immediately after a modal verb must always be in the base form with nothing added. This means no “-s” or “-es” for the third person singular, no “-d” or “-ed” for past forms, no past simple verbs, no past participles, and no “-ing.” For example, we say “She should study” and not “She should studies” or “She should studied.” Negatives and questions are made directly with the modal, as in “Should we start?” or “He must not enter.”
Past or Present
Modal verbs can indicate different times depending on how they are combined with the main verb. When a modal is followed directly by the base form of the main verb (verb 1), it usually refers to the present or future. For example, She can speak French suggests she has the ability now, and They should arrive soon refers to a future expectation.
To talk about past events, we use the structure modal + have + past participle (verb 3). This allows the speaker to express what was possible, necessary, permitted, or likely in the past. For instance, She could have studied harder shows that studying harder was possible in the past, and He must have missed the train indicates a deduction about a past event.
Modal verb + V1 = present or future
Example: I should leave now.
Modal verb + have + V3 = past
Example: I should have left earlier last night.
Why Do We Use Modal Verbs?
1. Permissions and Requests
A very common use of modal verbs is to ask for permission, give permission, or make polite requests. Modals help soften the tone of a sentence, making it more courteous or less direct than a simple statement or command. Depending on the context, the same modal can serve different functions: it can indicate formality, politeness, or obligation in the interaction.
Examples (Asking for Permission):
Can I borrow your book for a week?
May I leave the room for a moment?
Could I ask a question about the homework?
Might I sit here if the other seats are taken?
Examples (Giving Permission):
You can use my notes if you need them.
Yes, you may take the day off tomorrow.
You could start the project now if you like.
Students might submit their assignments a day late under certain circumstances.
Examples (Making Requests):
Could you pass the salt, please?
Would you mind closing the window?
Can you help me carry these boxes?
Might I ask you to review my essay?
2. Advice
Modal verbs are often used to give advice or make suggestions. Using a modal instead of a simple statement makes the recommendation sound softer and more polite, rather than commanding someone what to do. Different modals can signal varying degrees of urgency or formality.
Examples (Giving Advice):
You should see a doctor if you look unhealthy.
You should take a few deep breaths when you are stressed.
You should drink more water every day.
You can listen to your favorite music when you are sad.
You can try cooking a new recipe to improve your mood.
You might try meditating for a few minutes when you feel anxious.
You should eat more vegetables.
If you are tired, you should get some sleep.
If you are feeling depressed, you should go for a walk.
If you are bored, you could call a friend.
If you are feeling depressed, you should stop binge-watching Netflix while eating junk food.
If you feel anxious before a meeting, you can take a short walk to calm down.
3. Assumption
We can use modal verbs to make guesses or assumptions about something we do not know for sure. This can be about the present or the future (modal + verb 1), or the past (modal + have + past participle). Modals help us show how certain or likely we think something is. For example, must expresses a strong guess or near certainty, might and may show a weaker guess, and could suggests a possible but less certain option.
Present Examples:
He isn’t paying attention. He must be distracted.
The house is near the airport. It must be very noisy.
She looks tired. She might need some rest.
He left the keys on the table. He could be planning to go out soon.
The lights are off in the office. They might have finished work early.
The students are quiet. They may be working on the assignment.
She is smiling. She must be happy about something.
Past Examples:
He left the lesson early. He must have been sick.
The house was near the airport. It must have been noisy.
She didn’t reply to the email. She might have been busy.
He didn’t come to the party. He could have forgotten about it.
The streets are wet (now). It must have rained last night.
The streets were wet (when I went for a walk this morning). It must have rained last night.
They arrived late. They may have missed the bus.
He looked exhausted. He must have been working hard all day.
4. Obligation
Modal verbs can express that an action is necessary, required, or expected. They allow the speaker to show rules, duties, or strong recommendations. Must is used to indicate a strong requirement or something that cannot be ignored, while should expresses advice or a recommended action rather than an absolute rule. Will can also show a sense of commitment or determination in formal contexts.
Examples:
He must wear a helmet while riding his bike. (strong requirement)
You should submit the report by Friday. (recommended action)
She must finish her training before starting the new role. (necessary action)
We should respect other people’s opinions. (advice/recommendation)
He must not disclose confidential information. (strong obligation in the negative)
Employees will follow the company safety guidelines. (formal commitment)
Students must attend all lectures. (rule or requirement)
Using “Have to” for Obligation
In addition to modal verbs like must and should, English also uses “have to” to express obligation. “Have to” is more flexible than must and can be used in the past, present, and future. You can also use variations like “had to” for past obligations and “will have to” for future obligations. The meaning is generally similar to the obligations expressed with must, but it often refers to external rules, circumstances, or practical necessity rather than the speaker’s personal view.
Examples:
Past obligation: I had to open the store at 7am every day when I worked there.
Present obligation: I have to clean the floors every night after the customers leave.
Future obligation: I will have to report to my supervisor every day when I start working in this new company.
Note: In the example “I had to open the store at 7am every day when I worked there,” the speaker is expressing a past obligation. Saying “I must have opened the store at 7am every day” is different; it would be a guess, similar to the ones mentioned in the previous category, about what probably happened in the past rather than a statement of obligation.
5. Ability
Modal verbs are used to express a person’s ability to do something. For present or general future ability, we use can + base verb (V1). For past ability that actually happened, we use could + V1. Be careful: could have + V3 in this category does not describe past ability that actually occurred; it describes something that was possible but did not happen.
Examples (Present/Future Ability):
She can swim very fast.
He can speak three languages.
I can help you tomorrow.
They can finish the project on time.
We can solve this problem together.
You can rely on her for support.
Examples (Past Ability):
She could run very quickly when she was younger.
He could solve difficult problems easily.
They could not attend the meeting last week.
I could stay up late when I was a student.
We could lift the heavy boxes by ourselves.
She could understand complex math concepts as a child.
Examples (Past Possibility That Did Not Happen):
You could have called me, but you didn’t.
He could have solved the problem, but he chose not to.
They could have attended the concert, but they stayed home.
I could have finished the project yesterday, but I ran out of time.
6. Possibility
And finally, modal verbs can also be used to express possibility, showing that something can or might happen, without stating it as a fact. This use allows the speaker to indicate different degrees of likelihood.
Examples:
She might arrive later than expected.
It could rain this afternoon.
He may be able to join the meeting tomorrow.
The package may arrive tomorrow.
Examples from the TOEFL Test
Question 1
The following example is designed for TOEFL Reading Practice Test #23 – Coevolution of Pinyon Pines and Pinyon Jays.
Reading Passage: Attracting seed predators would not seem to be a successful survival strategy for pinyon pines. However, pinyon jays are behaviorally adapted to bury any seeds in excess of their immediate survival needs. This is a useful behavior for the jays, providing they can retrieve some of the buried seeds during winter, and good for the trees, as the unretrieved seeds are ready to germinate. Still, for the jays to bury any seeds, there must be an abundance of seeds far beyond the jays’ immediate needs. One tree could never produce so many seeds, but if all the pinyons in a region produced heavy seed crops at once, they would indeed “flood the market” with vastly more pinyon seeds than the local population of jays could consume. In fact, that is exactly what the pinyon pines do.
Question: According to the paragraph, why can a single pinyon tree not ensure that seeds are left uneaten to germinate?
A. Because seed coats are too thin and are always digested by the jays.
B. Because the jays bury only the seeds that they cannot immediately consume.
C. Because one tree cannot produce enough seeds to exceed the needs of the jays.
D. Because only large groups of trees are able to photosynthesize effectively.
Correct Answer: C
Explanation: The passage states explicitly: “One tree could never produce so many seeds…”. This makes clear that a single tree’s seed production is insufficient to overwhelm the jays’ consumption. Only when many trees produce simultaneously can the supply exceed the demand, leaving uneaten seeds to germinate.
The writer has used “could never” here to express impossibility, showing that the likelihood of one tree producing enough seeds is not just low but zero. This contrasts with modal verbs like “could” (possibility) or “might” (probability), emphasizing absolute lack of feasibility in this context.
Option A is wrong because seed coat thickness is not relevant here. Option B misrepresents the point—jays do bury seeds, but the issue is whether there are enough seeds in the first place. Option D is irrelevant, as photosynthesis is not the limiting factor described in the paragraph.
Question 2
The following example is designed for TOEFL Reading Practice Test #41 – The Formation and Distribution of Petroleum.
Reading Passage: How much oil is there in the world? This is an extremely controversial question. Many billions of barrels of oil have already been pumped out of the ground. A lot of additional oil has been located by drilling but is still waiting to be pumped out. A great deal more oil may remain to be found by drilling. Unlike coal, the volume of which can be accurately estimated, the volume of undiscovered oil can only be guessed at. Knowing how much oil has been found in an intensively drilled area, experts can make estimates of probable volumes in other regions where rock types and structures are similar.
Question: Based on the paragraph, what can be inferred about the total volumes of coal and oil in the world?
A. The total volumes of both coal and oil are known with reasonable accuracy.
B. The total volumes of both coal and oil are unknown and can only be guessed at.
C. The total volume of coal can be estimated accurately, but the total volume of undiscovered oil is uncertain.
D. The total volume of oil can be estimated accurately, but the total volume of coal is uncertain.
Correct Answer: C
Explanation: The passage contrasts coal and oil using modal verbs: “can be accurately estimated” for coal and “can only be guessed at” for oil. This indicates that experts have a reasonably precise idea of coal reserves, whereas the amount of undiscovered oil remains uncertain. Option C correctly reflects this distinction. Options A and B misrepresent the relative certainty of the two resources, while Option D reverses the comparison.
Test Your English Grammar Knowledge: Modal Verbs (Quiz)
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