We use Infinitives without the word to when they come after modals:
Infinitives have two forms:
There are three uses of the word to before the Infinitive:
You should
it is forbidden
1. To indicate an intention 2. After specific main verbs like agree, forbid, fail, begin, choose, decide, prepare, try, want, etc. 3. After specific adjectives
Can, could, may, might, shall, would, should, and must.
to play in the park right now.
study to get a 10 at the exam.
with to before the verb, and without to.