i-adjective
metallic smell; metallic taste
Describes something that smells or tastes like metal, such as coins, blood, or rusty water.
この水は金臭い。
This water tastes metallic.
手に金臭いにおいがついた。
My hands smell metallic.
金属臭 is a noun meaning 'metallic odor,' while 金臭い is an adjective describing the smell or taste itself.
Compound of 金 (kana, 'metal') + 臭い (kusai, 'smelly'). The exact historical derivation is uncertain, but the word transparently means 'metal-smelling.'