to 的用法

There are three types of format:

(I) main verb + object + [verb-ing] ~ present participle
She felt her heart beating fast.

(II) main verb + object + [to + verb] ~ infinitive with “to”
I don't want you to talk with her.

(III) main verb + object + [verb] the base form of verb ~ infinitive without “to”
Let us pray.

何時用那種, 要看 main verb 是什麼字和句子意思
因為你提到 let, make, see, watch, hear 猜你要 type (III)

Infinitive without “to” (Bare infinitive)

LET
Let him have a drink. (“have” ~ bare infinitive)
Mr. Chan lets Tom go to the toilet. (“go” ~ bare infinitive)

MAKE
The official made me fill out a form. (“fill” ~ bare infinitive)

HAVE
I shall have the porter bring up your bags. (“bring” ~ bare infinitive)

HELP
Who can help me settle down? (“settle” ~ bare infinitive)

Some verbs of perception can have an object and an infinitive without ‘to”.

SEE, HEAR, WATCH, FEEL, NOTICE
Did you see anyone leave the building?
I heard someone knock the door.
I watched him go.
She felt someone touch her on the shoulder.
Did you notice him pause?

Know the difference:
See/Hear someone do something
See/Hear someone doing something

Somebody did something. I saw that. I saw the complete action from the beginning to the end.
I saw Tom get into his car.

I heard them play the fifth symphony. (I heard the complete symphony.)

Somebody was doing something. I saw that when someone was in the middle of doing it. This does not mean I saw the complete action.
I saw Mary waiting for a bus.

As I walked past the church, I heard someone playing ‘Messiah’ on the organ.
(The person was in the middle of playing when I walked past.)

A few verbs can be followed directly by bare infinitive in fairly idiomatic phrases,
make believe, make do, let go

I tried to make believe she was happy, but knew deeply down it wasn’t true.
She refused to let go of her bag.