Remember that there are many types of modals
For example: should, ought to,might, may

1. Function
Modals are quasi-auxiliary helper verbs that are used to change the tone of a sentence.
2. Compare
I wear nice clothes.
I should wear nice clothes.
Modals introduce a new modality in a sentence. They change the tone.
3. Using modals
Structure: subject + modal + infinitive verb (without to)
I might go to the movie.
She should go to school.

4. What do the modals change?
May: describes possibility and permission.
Might: describes possibility.
Should: describes obligation and suggestion.
Ought to: describes obligation. (exactly like should)
5. Examples
You may come in. (meaning that you have the permission)
You should apply for that new job. (meaning suggestion)
You ought to pick up the children. (meaning that you are obliged)
Alex might go to the USA next year. (meaning possibility)