In English, we use modal verbs to express ability, authorization or a degree of certainty. There are always followed by a verb in the infinitive We will see some of them: can/could, may/might, must, shall/will, should/ought to.
We use can or could to express ability. It could be replaced by “to be able to”: I can swim; She could do that perfectly; He can cook.
We use may/might to express a possibility in the future: I may start my own business; She might write her first book; He might study more.
We use must to express an obligation: You must go to bed early; She must do her homework; He must do some sport.
We use shall/will to formulate a hypothesis or make an inference: I will be a talented speaker in the future; I shall graduate very soon; I shall change this habit.
We use should/ought to, to give advice or make a suggestion: You should be on time; I ought to be careful while driving; She should try this food speciality.
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