Modal Verbs

Should – Must – Have to

FormulationShould and Must are real modal verbs, and therefore, like all modal verbs:

They are always followed by the “Infinitive without to”.

Should do, Must do

They are the same for all the pronouns:

I should, he should, it should etc.

Formulation

Should and Must are real modal verbs, and therefore, like all modal verbs:

Do not need auxiliaries. They take direct negative and question forms

I Should not (Shouldn´t). We must not (mustn´t)

Should I? Must we?

Never combine with another modal verb:

You should can You should be able to… He will must He will have to…

Formulation

“Have to” is a semi-modal verb. It is like a modal verb because it fulfils specific function, but it behaves like an ordinary verb in its formulation:

It is followed by the infinitive “Without to”:

Have to do

It is conjugated according to pronouns:

I have to, he has to, etc.

Formulation

“Have to” is a semi-modal verb. It is like a modal verb because it fulfils specific function, but it behaves like an ordinary verb in its formulation:

It needs auxiliaries. It doesn´t take direct negative and question forms

I don´t have to . She doesn´t have to

Do I have to? Does she have to?

It can combine whit modal verbs:

You will have to, he might have to.

Usage - Should

I believe teachers should have higher salaries.

You look Tired. I think you should have some rest.

He shouldn´t make a rushed decision.

Do you think we should phone her?

What should I say when I speak to him?

1. Expressing an opinion/giving advice or asking for advice.

Usage - Should

He should arrive any minute.

He should be long now.

He shouldn´t have arrived by now.

2. Expressing an expectation

Usage - Should

You should have been more careful.

I shouldn´t have said that.

3. Expressing a regret about a past action

Usage - Should

Note 1:

“Ought to” is a synonym for “should”. It generally sounds more formal than “should”, and is less commonly used particularly in the question form:

Usage - Should

Note 2:

Should (but not Ought to ) is also express a small possibility.

- If I should ever go back there, I will not make the same mistake again.

- Should you need any further assistance, do not hesitate to contact me. (Formal writing)

Usage - Must

He is very ill. You must call a doctor now.

We must not (mustn´t) lose the match tomorrow, or we will be out of the tournament.

This is the best book I´ve ever read. You must read too.

You mustn´t hesitate to call me if you need help.

1. Expressing a necessity felt by the speaker (present or future)

Usage - Must

You must not (mustn´t) use your mobile devices during take off.

You must not be late for your interview tomorrow.

2. Expressing a prohibition (present or future)

Usage - Must

You must be tired after your very long day.

He must have read my letter, because he repeated exactly what I had written.

3. Expressing an assumption in the present or past (affirmative sentences only)

Usage – Have to

You have to make an appointment to see him.

She has failed her exam. She Has to retake it.

1. Expressing an external obligation (positive sentences)

Usage – Have to

He was very ill, had to call the doctor immediately.

He was very busy, I Had to make an appointment to see him.

2. Expressing a necessity or obligation in the past

Usage – Have to

He feels much better now, you don´t have to call a doctor.

I didn´t have to make an appointment to see him.

She has passed her exam, she won´t have to retake it.

3. Removing a necessity or an obligation (Present, past, future)

Usage - Have to

Note 1:

As you can see, the main difference between

“must”

And “Have to” is that “must” is a necessity felt by

the speaker, whereas “have to” is an external

obligation or rule. If this difference is not relevant,

you can use “must” and “have to”,

Interchangeably in positive sentences.

Usage - Have to

Note 1:

However, be careful that in the negative “must

not”

Is still a necessity or an obligation “NOT TO”

do something (a prohibition), whereas “don´t

have to”, removes the necessity or obligation.

Usage - Have to

Note 2:

As “must” has no past tense, both

obligation and

necessity are expressed whit “had to” in

the past.

Usage - Have to

Note 3:“Need to” is a softer alternative to both, “must” and “have to”:- I must/need to finish this tonight, because I want to take tomorrow off.

- I have to/need to finish this tonight. My deadline is tomorrow.

- Do I need to finish this tonight? I don´t need to finish this tonight.

Usage - Have to

Note 3:You may also come across the modal verb “Need ”. It is a very common modal verb, and can only be used in negative sentences and questions:

- Do I need to finish this? = need I finish this?

- I don´t need to finish this = I needn´t to finish this.

Gap filling exercise

Have you had your exam results?

Yes, I've failed biology. I will ………………..…..retake it in august.

Oh sorry. You ……….. be pretty upset. What about physics?I´ve passed that but with very low mark. My teacher thinks I ……………….retake that too.

Gap filling exercise

Have you had your exam results?

Yes, I've failed biology. I will have to (need to) retake it in august.

Oh sorry. You must be pretty upset. What about physics?I´ve passed that but with very low mark. My teacher thinks I should (Ought to) retake that too.

Gap filling exercise

Do you think you ……………………retake it?

No. I strongly feel that I must …………focus on biology. I …………fail that one. I …………………..get at least a 8 in biology to study medicine at university.

Did you fail biology last year as well?

No. I passed in last year. I ………………….have passed it this year too. I just didn´t study enough.

Gap filling exercise

Do you think you should (ought to) retake it?

No. I strongly feel that I must (need to) focus on biology. I mustn´t fail that one. I have to (need to) get at least a 8 in biology to study medicine at university.

Did you fail biology last year as well?

No. I passed in last year. I should (ought to) have passed it this year too. I just didn´t study enough.

Gap filling exercise

You ……..have studied enough! You always do.The exam …….. have been difficult.

No, the exam wasn´t difficult. I was too tired.I ………………………....... have partied the night before. I ………………………have studied instead.

Oh, I see. Well, you are good at biology.You ……………………...be able to pass it in august.

Gap filling exercise

You must have studied enough! You always do.The exam must have been difficult.

No, the exam wasn´t difficult. I was too tired.I shouldn´t (Oughtn´t to) have partied the night before. I should (ought to) have studied instead.

Oh, I see. Well, you are good at biology.You should (ought to) be able to pass it in august.

Gap filling exercise

I hope so. I ……………….………….find a summer job as well. My dad insist!

Did you have a summer job last year?

No. I didn´t ……………………. work last summer.I have some savings then.

What happen to your savings?

Gap filling exercise

I hope so. I will have to (need to) find a summer job as well. My dad insist!

Did you have a summer job last year?

No. I didn´t have to (need to) work last summer.I have some savings then.

What happen to your savings?

Gap filling exercise

I had to buy a car because my flat was too far from the college.

Well. Good luck with your retake. You must let me know how it went.