Helping Students with Modals
Michael Thompson
  When asking students to learn modal auxiliaries and modal equivalents, ESL/EFL teachers are asking them to learn how to form these modals correctly, recognize categories of modality, and choose the appropriate modal for expressing modality. These activities are desgined to help students learn to master the intricacies of English modals. These activities are desgined to help students learn to master the intricacies of English modals in three areas: forming modals, recognizing categories of modality, and using modals to express modality.
Introduction
We ask our students to learn a lot when we ask them to learn modal auxiliaries and modal equivalents. There are, first of all, the myriad forms taken by the various modals, some of which have subtle distinctions. Students need to become comfortable with the fact that can does not take the auxiliary do in a question (no *do you can speak Spanish?) while have to does (no *Have you to go to Rome?).
More important is that modals are distinguished from other auxiliaries by the fact that they have meaning. Students, therefore, need to become comfortable not only with the grammatical properties of modals, but their semantic properties as well. This is complicated by the fact that there is more than one category of meaning and the same modals are often used in more than one.
The first category -- called "deontic modality" -- is used to perform speech acts, such as offering, requesting, granting permission, commanding, etc.. When I tell my son, "You must be home by 10 o`clock." I am using deontic modality.
The second category -- epistemic modality -- is used to express the speaker`s opinion about the truth of a proposition. When I say, "You must be Rachel Thorne. You look just like your sister." I am saying that I am certain that the proposition "you are Rachel Thorne" is true.
A third category of modality is a bit more elusive. One characteristic of both deontic and epistemic modality is that the modals are connected with the speaker, not just the subject. With deontic modality, the modal refers to what the speaker is doing with the sentence. With epistemic modality, the modal refers to how the speaker sees the proposition. The third category -- sometimes called "dynamic modality" -- is more subject-oriented. "Rosa can run a mile in under five minutes." refers to one of Rosa`s abilities; it does not give information about the speaker.
A third hurdle for English-language students is that not all languages prefer to use modals to express these ideas. Modality is often expressed with other forms of speech. "You are obliged to be home by 10 o`clock", "I am certain that you are Rachel Thorne. You look just like your sister.", and "Rosa is capable of running a mile in under five minutes." all express the ideas explored, and if they sound stilted it is only because English has a preference for modal verbs rather than modal adjectives.
Re-phrasing
One of the most direct methods for providing experience with modals is to ask to students to re-phrase sentences. This can be done either as a speaking or writing exercise, and offers an advantage over more traditional cloze exercises in that the context is not open to interpretation. Such interpretations of context are common (I think the sentence refers to an obligation, but the student thinks it refers to a suggestion), and make it difficult to evaluate whether the student is using the modal correctly (i.e., is he using should because he thinks that the sentence refers to a suggestion or because he thinks should is used to express obligation?).
Generally with re-phrasing, students are given a sentence which expresses modality without using a modal. They are then asked to re-phrase this sentence, using the appropriate modal. One example would be:  
I am reasonably certain that Francesca is home. Francesca __________________. (should be home)
However, there is no reason the presentation cannot be reversed, with students being asked to re-phrase a sentence that contains a modal.
A variation which might be helpful for lower-level classes would be to give students a choice of three possible re-phrases.  
I am reasonably certain that Francesca is home.   a. Francesca should be home.   b. Francesca doesn`t have to be home.   c. Francesca must be home.
Role Plays
In this activity, students are divided into pairs, and each pair is given a situation.
The situation might be:
"Student A, you want to go to a concert with your friends. Please ask Student B for permission. Student B, you are worried about Student A going to the concert. Negotiate with Student A and command him be home at a specific time."
Another situation might be:
"Student A, you are going to a business meeting in Tokyo with Student B. Please discuss your trip with him and say when you expect the meeting to start and finish, and when you expect to return home. Student B