A modal verb is a verb which is used with another verb to express such ideas as possibility, ability, and necessity, e.g. computers can perform a wide range of tasks. Modal verbs in English can present some difficulties for learners. They occur quite frequently in the academic context and the range and variety of their use can make understanding and using them correctly quite a challenge.
The nine main modal verbs express a range of meanings, which may differ very subtly.
Modal verbs are used to indicate the writer's or speaker's attitude to what he or she is writing or saying. There are three main categories of meaning.
Expressing possibility, ability and permission
The most common meaning for modal verbs in the category of possibility, ability and permission is logical possibility: indicating what is or is not possible from what we know about a situation. All four modals in this category (can, could, may, might) are used in this way.
Can is frequently used to indicate ability.
The use of can and may to ask or give someone permission is common in speech but rare in formal writing, because it involves personal interaction.
Expressing obligation and necessity, intention and prediction
In the category of modal verbs expressing obligation and necessity there are two main meanings found in formal writing. The first meaning is that of personal obligation; the writer states what he/she and perhaps the reader is obliged to do/believe etc. using a modal verb such as must or should.
The second meaning is that of logical necessity; the writer states what he/she wants the reader to conclude from the information presented using a modal verb such as must or should.
Using modal verbs to express intention and prediction clearly relates to future time. This is a large and complex area of English grammar, and here the focus is on the modals will, would and shall; how they are used and how they can be distinguished.
will and would are commonly used in formal writing to predict future events or states that are not caused by anyone. Very often the period or point in time is not mentioned.
shall is used to indicate the writer's personal intention. This is a formal and conventional use of this modal.
Helpful sites for practice
Online grammar explanations with examples.
Grammar explanation links to practice exercises and a useful verb list.
Detailed information with practice in this area of grammar.
A comprehensive set of resources for grammar. Provided by Monash University, Australia.
A reference list of common dependent prepositions.
British Council Learnenglish Grammar Games
Grammar games to practise most aspects of grammar.
Test your knowledge of grammar terminology by matching examples to grammar terms.
A comprehensive online glossary of grammatical terms.
Grammar practice website.
Grammar practice website.
SOURCE: The Open University, 2011