BUR #26208 is pending approval.
deprecate metal
Potentially controversial. I consider this tag not to be ambiguous and not useful. This has been randomly used on posts depicting misc. metallic objects. Such as on post #2209476 (bucket and drum (container)) or random images of armor.
Metal also has been used on posts depicting metal ingots like post #1992793.
Anyways, I think steel ingot should be better renamed into metal_ingot. Because without more detailed explanation or context of usage, not all metal with silvery grey color is steel or iron.
Despite so, I consider gold should rather stay because its purpose is to describe any objects made of gold. Unlike the more generic, overly-broad metal.
UPDATE: Perhaps for situations like on post #3524116, something like metallic_object as a tag sounds better-suited for random, unspecified metallic stuff. (iron itself is deprecated).
Updated