en_tn/job/37/18.md

Can you spread out the sky ... a mirror of cast metal?

Elihu asks this question to emphasize that Job cannot do this. Alternate translation: "You cannot spread out the sky ... a mirror of cast metal." (See: rc://en/ta/man/jit/figs-rquestion)

as strong as a mirror of cast metal

In biblical days, mirrors were made of metal. Elihu speaks of the sky giving no rain as if it were as hard as solid metal. (See: rc://en/ta/man/jit/figs-metaphor)

cast metal

This refers to metal that is melted, poured into a mold, and then hardens as it cools.