Modal Verbs for Expectation: Should, Will, Must & More

Hello English learners, and welcome to a new lesson! In today’s lesson, we will learn about modal verbs for expectation.

How do you say that you expect something to happen, but you are not completely certain? English gives us several useful modal verbs and expressions, including should, ought to, will, must, be supposed to and be bound to.

However, they do not all express the same kind of expectation. Some describe something that is likely, some refer to a plan or arrangement, and others express a strong conclusion based on evidence.

In this lesson, we will look at the differences and learn how to choose the most natural expression for each situation.

Grammar note: Be supposed to and be bound to are not modal verbs in the strict grammatical sense, but they behave like modal expressions and are commonly taught alongside modal verbs.

Table of Contents

Should – a reasonable expectation

We often use should when we expect something to happen because it seems likely, normal, reasonable or planned.

Form

subject + should + base verb

The train should arrive at about 7.45.
The new restaurant should be good – it has had excellent reviews.
There shouldn’t be too much traffic at this time of day.

Here, should does not mean that something is guaranteed. It means that, based on what we know, we have good reason to expect it.

Compare:

The parcel will arrive tomorrow. → the speaker sounds very confident.
The parcel should arrive tomorrow. → this is expected, but there is still some uncertainty.

Should have + past participle

We can also use should have + past participle when something was expected to happen before now.

The train should have arrived by now.
They should have received our application yesterday.

This does not necessarily mean that the expected event actually happened.

Ought to – similar to should

Ought to is very similar to should when we are talking about expectation.

The weather ought to improve by the weekend.
She ought to know the answer – she’s worked here for ten years.
The repairs ought to be finished by Friday.

In modern English, should is considerably more common, especially in conversation.

Ought to can sound slightly more formal or traditional, but it is still perfectly correct.

Negative form

The negative is ought not to, although shouldn’t is much more common in everyday English.

The journey ought not to take more than three hours.

Past expectation

We can also use:

ought to have + past participle

They ought to have arrived by now.

Be supposed to – plans, arrangements and expectations

We use be supposed to when something is expected because of a plan, arrangement, rule or social convention.

Form

subject + be + supposed to + base verb

I’m supposed to meet Daniel at six.
The conference is supposed to start at nine.
We’re supposed to receive the results next week.

Notice that be supposed to can describe several slightly different ideas.

1. An arrangement

I’m supposed to meet Helen after work.

There is already a plan.

2. A rule or duty

Students are supposed to submit their assignments online.
You’re supposed to wear a seat belt.

Here it means something similar to be expected or required to.

3. What people say or believe

That restaurant is supposed to be excellent.
The new series is supposed to be very good.

Here, be supposed to means that this is what people generally say or believe.

When the plan does not happen

We often use was/were supposed to when an arrangement existed but did not happen.

I was supposed to call her yesterday, but I completely forgot.
We were supposed to leave at eight, but the car wouldn’t start.

Be supposed to vs should

Compare:

The train is supposed to arrive at 8.10.
→ According to the timetable or plan.
The train should arrive at 8.10.
→ I expect that it probably will.

modal verbs for expectation

Be bound to – a very strong expectation

We use be bound to when we believe something is extremely likely or practically inevitable.

Form

subject + be + bound to + base verb

She’s bound to notice the mistake eventually.
He’s bound to do well in the interview.
With so much traffic, we’re bound to be late.

Be bound to is stronger than should.

Compare:

She should pass the exam. → I think she probably will.
She’s bound to pass the exam. → I feel almost certain she will.

Will – confident expectation or prediction

We often use will when we are confident about what will happen.

Don’t worry. The children will be fine.
You’ll love this book.
There’ll be plenty of food.

In these examples, will expresses the speaker’s confident prediction or belief.

It can also describe behaviour that we expect because it is typical of someone.

Ask Robert. He’ll know what to do.
Emma will usually arrive early.
That’ll be James at the door.

The last example is particularly interesting. The speaker hears the door and confidently assumes who it is.

Must – a logical conclusion

Must is slightly different from the other expressions in this lesson.

We use must when the evidence makes us believe that something is almost certainly true.

Present deduction

must + base verb

You’ve been working since six this morning. You must be exhausted.
Nobody is answering. They must be out.

We are not predicting what will happen. We are drawing a conclusion from the evidence available now.

Past deduction

must have + past participle

They left at six, so they must have arrived by now.
She didn’t answer my message. She must have been busy.

Negative deduction: can’t, not mustn’t

A very common mistake is using mustn’t for a negative deduction.

Use can’t or couldn’t instead.

✅ That can’t be right.
✅ She can’t be at home – I just saw her in town.
❌ ~~That mustn’t be right.~~

Mustn’t normally means prohibition:

You mustn’t use your phone during the exam.

Modal Verbs for Expectation: Quick Comparison

Look at how changing the expression changes the meaning.

The train arrives at 8.00.

The train is supposed to arrive at 8.00.

According to the timetable, that is the planned arrival time.

The train should arrive at 8.00.

I expect it to arrive then.

The train will arrive at 8.00.

I am confident that this will happen.

The train is bound to be late.

Circumstances make me feel almost certain that it will be late.

The train must be late.

I have evidence now that makes me conclude it is late.

Which modal verb should you use for expectation?
Use should or ought to for something you reasonably expect, be supposed to for a plan or arrangement, be bound to for something you consider highly likely, will for a confident prediction, and must when evidence leads you to a logical conclusion.

Modal Verbs for Expectation Practice Worksheet

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