Modal verbs are a special class of verbs in English grammar that express the speaker's attitude, will, possibility, or necessity. Modal verbs grammatically and semantically provide additional information to the expressor rather than just conveying the main message of the sentence.
There are many types of modal verbs, and here are some of the common modal verbs:
1.can: indicates capability or possibility. For example, "i can swim."(I can swim.) ）
2.Could: Indicates a past ability or possibility. For example, "he could h**e done it."(He probably already did.) ）
3.may: indicates the possibility or allow. For example, "You may go now."(You can go now.) ）
4.might: indicates the likelihood of the past. For example, "it might rain later."(It may rain in a while.) ）
5.shall: Indicates an order, request, or request for the opinion of the other party. For example, "shall we go for a walk?".(Shall we go for a walk?)）
6.should: Indicates that something should be done. For example, "you should eat more vegetables."(You should eat more vegetables.) ）
7.will: indicates what you are going to do. For example, "I will call you later."(I'll call you ** later.)
8.would: Indicates that something will be done in the past. For example, "He would help me with my homework."(He'll help me with my homework.) ）
9.ought to: means that something should be done. For example, "You ought to apologize for what you did."(You should apologize for what you did.) ）
10.had better: Indicates that it is better to do something. For example, "You had better go home now."(You'd better go home now.) ）
The above are some common modal verbs, but not all. The use of modal verbs needs to be judged according to the context and the meaning expressed. At the same time, it should be noted that modal verbs are usually followed by verb forms, that is, modal verbs are followed by the basic form of the verb, not the form of the continuous or perfect tense.