We need modal verbs to express different levels of certainty and possibility. Also, we use them to speak about ability, to make requests and offers, to ask for permission, to express necessity or obligation.
There are 9 modal verbs in the English language. They all have their own meanings and differences in usage. That means, as a rule, we can not use them interchangeably.
At first, here is the list of modal verbs:
can - could (can't - couldn't)
may - might (may not - might not)
must (mustn't)
shall - should (shan't - shouldn't)
will - would (won't - wouldn't)
Some grammarians move the verb 'ought to' to a special place and call it semi-modal. We have dedicated a distinct article to this verb. You can read it here.
In addition, you can find separate articles about certain modal verbs here👇
- Modals of deduction
- Modals of ability
- Modals of obligation and advice
- Modals of permission
- Modals of requests
Now, let's focus on what modal verbs really are, their grammatical functions and general rules.
Modal verbs general facts
Modal verbs do not act like main verbs in a sentence. That is why, some grammarians call them defective. This aspect makes them easy to use. But you need to remember these simple rules of usage of modal verbs:
- modal verbs do not need an ending to show person, tense and number;
- modal verbs do not form participles and gerunds;
- modal verbs act like auxiliaries in questions;
- modal verbs can not be used alone without a main verb;
- main verb goes without particle 'to' after a modal verb.
Look at the examples below 👇
Mike can swim. - ability, without ending to show person, can+main verb without particle 'to'
Can Mike swim? - modal 'can' forms a question
Modal verbs and tenses
First of all we need to say that there is only one modal that has the future tense and there are only two modals that have the past tense.
We express future meaning by using such adverbs as 'tomorrow', 'next week', etc. Modal verbs 'will' and 'would' already have this meaning.
Mike will go to the GYM tomorrow.
I can go to the GYM with Mike tomorrow.
May I go to the GYM with Mike tomorrow?
We can use past forms of the modals 'can' and 'will' to talk about the past.
I can go to the GYM with Mike tomorrow. - Carol said that she could go to the GYM with Mike the next day.
I will go to the GYM with Mike tomorrow. - Carol said that she would go to the GYM with Mike the next day.
And once again, the main idea about modal verbs is that each verb has its own meaning and we choose each modal depending on the context. You can learn about modal verbs and their meanings more in the articles that were mentioned above.