Have you developed an approach to teaching modal verbs? I’ve found it most effective to focus on these three aspects:
- Function. What purpose(s) do these modal verbs serve? What do they express? Students will learn and retain grammar if they understand how it functions in communication. I strongly recommend presenting these auxiliary verbs in groups according to their communicative functions, the most basic ones being: necessity, certainty, and ability.
Consider the following as a guide:
(Note: I’ve included modal-like expressions.)
NECESSITY: must, have (got) to, cannot, be supposed to, had better, should, ought to, could, might, may
CERTAINTY: must, cannot, may, might, could, should, ought to, will, would
ABILITY: can, could, be able to
Other useful guides:
The Guide to Grammar and Writing by Capital Community College
Bob Wilson’s Grammar Aquarium
Once you’ve grouped the modal verbs according to their functions, you can then divide them further according to time frames. For example, we express a present ability with CAN and a past ability with COULD.
- Strength. Grammar books differ on the number of functions modal verbs have, but when you consider the aspect of strength, my three basic groupings hold true:
NECESSITY: must, have to (necessary)/ cannot (prohibited) > be supposed to (expected) > had better, should, ought to (advisable, with had better being very strong) > could, might (suggested) / may (permissible)
CERTAINTY: must , cannot, will ( nearly certain) > should, ought to, would (likely) > may, might, could (possible)
ABILITY: can, could, be able to (No difference in strength.)
- Formality. When teaching any language form, be sure to tell students about appropriacy. This applies to use of contractions (e.g., CANNOT v. CAN’T) and changes in pronunciation (/ʃʊd hæv/ v. /ʃʊd ə/). Explain that the level of formality can dictate a choice between two equivalent expressions. For example, when expressing certainty, HAVE TO is preferred in informal (spoken) English and MUST is generally used in formal speech. Furthermore, the degree of necessity or certainty may be weakened depending on how formal a relationship is. For instance, you may have a strong argument against your boss’s plan, but voicing it with certainty is disrespectful. Consider the difference: “That won’t work.” v. “That may not work.”