The “smell of metal” is actually a body odor caused by contact between skin and metal! We all know that musty smell that metal has, like pennies or other things made of copper, brass, and iron. It is actually caused by human body odor. It isn’t a metal vapor that causes the smell at all. 

Some researchers treated test subjects’ hands with a ferrous solution composed of iron dust, steel, and cast iron plates. All the subjects recognized the smell on their skin. Researchers then captured the smell and analyzed it with a glass funnel containing extraction fiber. The fiber was analyzed through gas chromatography. 

They discovered that the metallic smell is actually caused by sweat coming in contact with iron. The sweat actually corrodes the iron which generates reactive ferrous ions that break down lipid peroxides in the skin and creates odorous aldehydes and ketones. 

So, the smell is actually a reaction with our sweat. Now, when you smell a particularly raunchy jar of pennies, you can imagine all the nasty hands that made it stink so badly. Thanks science.