A modal verb is a helping verb. It gives us more information about the writer or speaker's attitude and thoughts. It shows us how strong their feelings are.
Modal verb verbs can show us:
Certainty - Are we sure?
Ability - Can we actually do it? Is it possible?
Possibility - Do we think it will happen? Is it likely to happen?
Willingness - Are we happy do do this?
Obligation - Do we have to?
Necessity - Do we you need to?
Example sentences: Certainty - I am absolutely certain that it she is telling the truth. Ability - I can do it, but only if the jump is set up correctly. Possibility - We might be able to make it. Willingness - We probably should start our homework… Obligation –You must be home by 10:00om at the latest. Necessity –We need to make sure we improve our lap times.