English modal verbs: can, could, will, would, may, might, must, shall, should
Their negatives: can’t, couldn’t, won’t (will not), wouldn’t, may not, might not, mustn’t, shan’t (shall not), shouldn’t
Other verbs or expressions that often function the same as modal verbs: ought to, have to, not have to, need to, need not, had better, had better not, dare
Normal verbs are usually actions; things that you can actually see somebody doing, and they can be used in all tenses.
Forms of normal verbs
I will refer to the simplest form of a verb, as a root verb.
Examples of root verbs: eat, sleep, run, cook, think, feel
I will refer to the form “to+root verb” as an infinitive.
Examples of infinitives: to eat, to sleep, to run, to cook, to think, to feel
I will refer to a verb ending with “-ing” as a gerund.
Examples of gerunds: eating, sleeping, running, cooking, thinking, feeling
Modal verbs can only be followed by root verbs.
modal verb + root verb
Usher can sing and dance at the same time. = (can + root verb)
I can’t complete this task alone. = (can’t + root verb)
I’m sure that he would agree if you asked him politely. = (would + root verb)
You should see a doctor as soon as possible. = (should + root verb)
You may use my desk while I am away. = (may + root verb)
There’s a good chance that she might change her mind. = (might + root verb)
Oleg must fetch the parcel instead of David. = (must + root verb)
We shall investigate the matter further. = (shall + root verb)
You had better walk faster, or you will certainly be late. = (had better + root verb)
You ought to call and let us know if you will not be able to make it on time. = (ought to + root verb)
I can’t to complete this task alone. = (modal + infinitive)
I can’t completing this task alone. = (modal + gerund)
You should to see a doctor as soon as possible. = (modal + infinitive)
You should seeing a doctor as soon as possible. = (modal + gerund)