"Gold" can be used as a noun. (He paid in gold.) It can also be an adjective. (She won the gold medal.) "Golden" is an adjective. (She wore a golden necklace.) It is never a noun. It can have special meanings as well. (Those were the golden days of his youth- the best days of his youth')

The difference comes when trying to use either in context. Gold is a noun , verb. And adjective . Golden is mostly used as an adjective to describe something with the color of gold. E.g golden hair. Gold on the other hand is used to describe an object actually made of the substance (gold). E.g he had a gold lamp.

You’ve heard of the golden rule, haven’t you? Whoever has the gold makes the rules.

Gold is a noun (a naming word) Golden is an adjective (a describing word) E.g. I have gold in my pocket. (used as a noun) She has a golden heart. (used as an adjective)

noun vs. adjective