This questions seems based on out-dated theory of olefaction (which is the science of smells.)
In the old theory, the nose detects minute particles of a substance in air by receptors keyed for specific particles. These particles are assumed to be in the air because we can smell them.
This old theory can be refuted based on three observations:
- Compounds with different chemical compositions can smell
exactly the same. (creosol and eugenol)
- Compounds of different isotopes can smell different. (musk)
- Concentrations of compounds can change the odor completely. (phenol)
Since the advent of genetic technologies, a new theory is on the horizon is the underlying mechanism for smell is based on quantum oscillations. This theory is derived from information gathered from studying the genome which encodes the proteins responsible for the sense of smell.
The metallic smell does not come from metal. One current theory is the metal causes lipids on the skin to oxidize. The oxidized lipids are what travels to the nose. The nose is actually picking up a human scent of blood at a very small concentration. Even at small concentrations, blood is something the which the nose is extremely sensitive.