The English language may seem to be fairly simple for a first language speaker, but when it comes to explaining the different parts of speech and their uses, even experienced speakers may find that that are at a loss for words. This is where a simple guide will come in handy – whether you are learning English or teaching it to someone else, the simple guide series will tell you everything you need to know. This one deals with modal auxiliary verbs.

What is a modal auxiliary verb?

Modal auxiliary verbs are also referred to as modal verbs or modals and are used before main verbs to add meaning to the main verbs e.g.

I will go there tomorrow (Will is a modal verb, it adds meaning to the main verb "go")

They must hurry or we will be late (Must is a modal verb, it adds meaning to the main verb "hurry")

What are the modal auxiliary verbs?

Can, could, may, might, shall, should, will, would, must, ought

Each modal verb adds meaning to a main verb in a different way, and many are used to show varying levels of politeness or formality e.g.

Can I use that?; May I use that? ("May" is more formal and polite)

Modal verbs usually come before the base form of an auxiliary verb or main verb (but sometimes a noun or adverb is placed between the modal verb and the base form of the auxiliary or main verbs) e.g.

I could start now; I could have finished earlier; They should just go (Just is an adverb placed before the base form of a main verb); Must I go? (Nouns are found between the modal verb and base form of the auxiliary or main verb when questions are asked)

Negative forms

Every modal has a negative form, and this is created by adding the modal + not. This usually creates two separate words, but contracted forms can also be created, and these forms are more common in spoken English (although either form is correct). Each modal is modified as follows:

Can = Cannot = Can't

Could = Could not = Couldn't

May = May not

Might = Might not = Mightn't (Mightn't is very rarely used)

Shall = Shall not = Shan't (All forms of shall are seen as formal language)

Should = Should not = Shouldn't

Will = Will not = Won't

Would = Would not = Wouldn't

Must = Must not = Mustn't

Modal auxiliary verbs used in the present and future tenses

Modals and the main verbs or auxiliary verbs that they are paired with can change according to the tense that is being used.

When using the present and future tenses, the modal verb remains the same and the verb that it modifies remains in its base form e.g.

I must go now; Can I call you tomorrow?; I will get to it when I have time

Note: When using the present continuous tense as a future tense, the auxiliary verb "be" changes form e.g."They are running next week" becomes "They might be running next week" (The auxiliary verb will almost always become "be")

Modal auxiliary verbs used in the past tense

When using modal verbs in the past tense, the word "have" is combined with the modal and the past perfect form of the main verb is used e.g.

I must have gone last week; Could I have called yesterday?; I would have gotten to it by the time you got back.

Note: The use of a modal + "have" overrides the use of "had" when dealing with the past tense (had changes to" have" to accommodate the modal, but the tense remains the past).

"Would" and "could" are exceptions, as they can both be used in the past tense without the need for "have" or for changing the base form of the verb e.g.

I would run a lot when I was younger; I could do it before but I forgot how

"Shall", "will" and "can" cannot be used in the past tense (although "could" is generally seen as the past tense form of "can").

Some common uses for modal auxiliary verbs

Modal auxiliary verbs add meaning to other verbs, and in doing this they modify the meaning of an entire sentence. They indicate the importance or nature of that what is being "done" in the sentence. We use modal verbs to indicate:

- What must (or mustn't) be done or what must (or mustn't) happen e.g.

They should get their act together, I must leave by lunchtime, He must not come here again

- What can or might happen, or what can't or might not happen e.g.

It might rain tomorrow, He shouldn't be here for at least another month, It will happen again

- That something is allowed or not allowed (permission or prohibition) e.g.

You can't go that way; I shall lend you my pen; He can go whenever he wants to

- That something can or cannot be done (such as one's ability) e.g.

I can speak English fluently; I could dance well when I was younger; He can play the violin

- That advice is being given e.g.

You should see a doctor; I would back off if I were you; They shouldn't be doing that

Terms and expressions that are used as modal verbs

There are some terms and expressions that are not true modal auxiliary verbs, but are often used in the place of modals as they perform the same function. These include: Have to, have got to, need to, ought to, be able to and more e.g.

I want to be able to play the guitar by the end of the year; I have to go, You need to hurry if you're going to make it

You may notice that an infinitive is clearly used with each of these terms (to + base form of verbs). Modals are used before infinitives but since these don't usually contain "to", they are called "zero infinitives". Terms that lead into infinitives, like those listed above, are the ones that can be used to replace modal verbs. These are sometimes needed to create the desired meaning and will be learnt as one gains experience with the language.

Keep it simple

Before academically learning modal verbs, a proper understanding of the English present, past and future tense system is needed – this will make the learning of modals much easier. An easy way to identify modal auxiliary verbs is to remember that they come before the infinitives of other verbs – this will help with the placement of other terms (that are not modals but can be used in the same way) as well. Take it one step at a time – and practice and experience will ensure that you remember all you need to know in no time.