Functions of Modal Auxiliary Verbs

June 30, 2021joelleva

Summary: This discusses one of the most important and versatile features discussed in 3/4 English Language, modal auxiliary verbs. These serve a range of functions and purposes. 

What is a modal verb?

One of the most important features of the English Language course is modal verbs. Modal auxiliary verbs (to give them their full name) are one of the most versatile language features that we discuss, and there are 9 main modals. These group nicely into 3 groups of 3, with the simple pneumonic: rhyme, match, triple M. 

Rhyme: could, would, should

Match: can, will, shall

Triple M: may, might, must

What do modal verbs do?

Now that we have established the words we are talking about, it is now important to discuss what they actually do. Remember, as I have said before and will say again, remember to SPECIFICALLY analyse what modals are doing in a specific text, and the more generic things I mention in this article are a useful guide as to what you should be looking out for and thinking about, but please remember that specificity is vital when you are analysing. 

Moreover, when you are analysing what a modal is doing, please ensure that you do not define the word as itself. For example, do not say something like, “will,” is used to indicate that an event will occur, but instead explain how it is used to express with a high degree of certainty that an event is going to occur.  

Types of modal verbs


This function is slightly different to all the others which I will discuss after this, although modal auxiliary verbs are actually very useful for achieving brevity and succinctness in a text. Whilst this is a function that modals serve almost regardless of where they appear, it is one that is especially useful when they are used to commence a question (usually yes/no). For example, “can you please…” is much more succinct than, “are you please able to…”. 

Express degrees of likelihood

A number of modals such as should, will, may, might, and could, work to express how likely something is. For example, will tends to be used to reflect a high degree of likelihood (also called certainty), whereas may, could, should, and might are all used to reflect lesser degrees of likelihood, and are often used to hedge.

Express ability or permission

Can and could are frequently used to express that someone has the ability (or is permitted) to do something, and may is commonly used to indicate permission. I don’t think that this requires significant explanation. 


I don’t think this requires too much explanation, but must and shall are particularly commonly used when trying to express that someone is obliged to act or refrain from acting in a particular way. Both of these tend to be used to indicate quite high degrees of obligation (actually amounting to compulsion). For example, section 137 of the Evidence Act 2008 (Vic), uses must indicate that if the evidence in a criminal proceeding is more unfairly prejudicial than it is of probative value, the judge is required to exclude it and declare it inadmissible. 

Moreover, should tends to be used for a slightly lesser degree of obligation, more indicating that a course of action is desirable or strongly preferred, but not necessarily compelled. 

Side note

When discussing the use of modals in texts, particularly something like terms and conditions, pay attention to how modals are often used to show lopsided degrees of obligation. For example, they may say something like, “patrons must…” indicating that they are under a high degree of obligation, whereas they can also then say something like, “if x occurs, the organiser may do y,” indicating an ability, but lessening the degree of obligation. 


This list of purposes is not even close to exhaustive, but remember to pay attention to what they are doing in the SPECIFIC TEXT THAT YOU ARE PROVIDED WITH.  

Anyway, I hope this article has been useful to you and your understanding of modal auxiliary verbs. 

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