Is “he was melting wax shaping to their minds” a metaphor?

Yes.

Explanation: While both similes and metaphors are used to make comparisons, the difference between similes and metaphors comes down to a word. Similes use the words like or as to compare things—“Life is like a box of chocolates.” In contrast, metaphors directly state a comparison—“Love is a battlefield.”

A metaphor is a figure of speech that describes an object or action in a way that isn’t literally true, but helps explain an idea or make a comparison.

Here are the basics:

A metaphor states that one thing is another thing

It equates those two things not because they actually are the same, but for the sake of comparison or symbolism

If you take a metaphor literally, it will probably sound very strange (are there actually any sheep, black or otherwise, in your family?)

Metaphors are used in poetry, literature, and anytime someone wants to add some color to their language