In ancient wars, people always wear iron helmets and iron armor to protect themselves. Some animals such as tortoises, crabs, and beetles will also grow hard exoskeleton armor to protect themselves, just like iron armor.
However, there is an animal with a real metal armor exoskeleton. This animal is Chrysomallon squamiferum. Chrysomallon squamiferum lives in the vents of deep-sea hot springs with high pressure, high temperature, strong acidity and low oxygen. Through anatomical research, it is found that it has evolved a volute of iron sulfide, which is the only organism in the world known to incorporate iron into its exoskeleton.
At present, scientists are studying this kind of animal with biological iron armor, looking forward to solving the "secret" of this animal in the future.