In English, a modal auxiliary verb is a special class of verb. It is a subgroup of auxiliary verbs -- or helping verbs -- that, when paired with another verb, expresses ability, permission, possibility or obligation. Modal verbs include "can," "could," "may," "might," "should," "must," "shall," "should," and "would." Teach modal verbs by introducing the function of the verb; provide plenty of examples for students to absorb their use and meaning.

Introduce Modal Verbs

Introduce the modal auxiliary verbs you will be covering by writing them on the board and explaining that a modal verb is used to affect or modify a verb that follows it. Explain that they are used to indicate possibility, suggestions, advice or obligation. Mark which verbs express which meaning. Pronounce each verb for the students slowly and have the students repeat them back to you.

Give a Basic Example

Give an example of how to construct a sentence using a basic modal verb, such as "can." An easy example would be “I can learn English,” where the verb expresses an ability. Explain that the verb that follows the modal verb must be in its basic or infinitive form minus the word “to.” Show an example using "he" or "she" to show that you do not add an s to modal verbs in the second person, unlike other verbs. "He should be quiet" and not "He shoulds be quiet."

Use Negative and Question Forms

Demonstrate how to use modal verbs in the negative and question forms by providing examples. Make sure you are clear that the word “not” must follow the modal verb and not the verb it modifies. Then show that to form a question, you simply invert the subject and the modal verb. For example: “Can you learn English?”

Demonstrate In-Depth

Compare and contrast the different meanings of basic modal verbs by providing examples of when they indicate possibility, or advice or obligation. Talk about what you "can" do versus what you "could" do to demonstrate how one verb expresses ability and the other expresses a future possibility. “I can do 50 sit ups.” “I could do 100 if I worked harder.” Point out that could is also the past tense of can. Then discuss things you "might" do after class, explaining that this verb is an uncertain possibility. “I might take a short nap.” Finally, discuss things you "should" do and things you "must" do in order to show students a modal verb that is a suggestion and one that expresses an obligation. “I should eat healthier,” is advice, while “I must pay my phone bill” is an obligation.

Make the Students Use the Verbs

Ask your students to provide their own examples by asking them guided questions. “What might you do this summer on vacation?” “What could you do with a million dollars?” Give suggestions for students to choose from initially and continue to do so if they seem confused or uncertain. Once they seem comfortable, begin to ask questions that produce a negative response: “Might you go to the moon tomorrow?”

Have Students Work Independently

Allow the students to independently produce sentences using modal verbs by putting them into groups and having them interview each other. Remind them how to construct a sentence using modal verbs. Have them use as many verbs as they can and encourage them to be creative with their questions and answers. Once they have finished their interview, have students read aloud their interview answers and correct for mistakes that pertain to modal verbs.