Let us ( me, them) + V. Why is the Verb without "to"? TIA

Ex:

Let’s (let us) go,

Let him speak

Let’s rock,

ets

I can’t find an answer. Why is the Verb (go, speak rock) without “to”?

And should I say? Is it correct?

“Let’s (to) walk quickly and (to) go home”.

If I’ve got it properly from my grammar books there are three moods in English, indicative, imperative and subjunctive.
“Let us go, let me do” could be the imperative mood.
The imperative mood asks the bare infinitive of the main verb with the verb let.

I am interested in additional explanation related to this matter.

Thanks

Hi,

When you use a verb after ‘let’ there is no need for the preposition ‘to’. It is necessary to have a direct object and in the example ‘Let’s’ this is a contraction of ‘Let us’. Other verbs such as ‘allow’ and permit’ (with a similar meaning) need a direct object and the preposition ‘to’ as in: Allow him/permit him to speak - in contrast to: Let him speak.

Alan