Albert Barnes Commentary Psalms 106:19

"They made a calf in Horeb, And worshipped a molten image." — Psalms 106:19 (ASV)

They made a calf in Horeb - (Exodus 32:4). Probably in resemblance of the Egyptian god “Apis.” The image was made by Aaron out of materials furnished by the people, and at their request (Exodus 32:1–3), so that it might be said to be the act of the people.

And worshipped the molten image - The word rendered “molten” is from a verb נסך nâsak - to pour, to pour out; hence, to cast, to found; and it means anything that is made by fusion or casting. This image was cast (Exodus 32:4), and hence, this name is given to it.