Completing a Sentence with the Correct Modal Verb

Modal Verbs are a very special type of verbs because they are always used in the same form – they don’t change to match their subjects. These modal verbs change the meaning of the main verb in some way, often by expressing advice, necessity, ability, expectation, permission, possibility, or an offer or a polite request.  

The main verb that follows a modal verb is always the “bare infinitive form” – the basic verb without “to” before it.

It can’t rain on my birthday!

We may not be able to have a party!

Should is used to express advice.

 

I really should clean up my room. (expresses advice—to oneself)