In the sentences Let's be out and let him out, why is out used as a predicative in the first sentence and in the second sentence?

The verb Be is usually followed by a slogan, which is a word indicating the nature or state of things, so Let's be out. The free translation is to let us go outside, and the literal expression commonly used in English is to let us outside; Let him In the sentence out. let is the verb of the imperative sentence, him is the object, and out is a word that complements the state of the object him, so it is called a complement.