Most things we smell are byproducts of chemical interactions. That distinctive metallic smell you get from handling pennies is the iron and copper reduction of lipids on your skin. The smell people associate with metal isn't actually metal, it's this volatile organic that has a very low detection threshold. Same for the smell of blood, you're not smelling blood or the iron in the haem, it's the breakdown of skin organics caused by a transition metal.
It's possible we're so sensitive to these metal-reduced organics because they let us smell blood, so there's an evolutionary selection pressure (for finding injured or dead dinners).
You could probably smell something in space, but it would be in a very cold vacuum, so you wouldn't have mucous membranes for very long. A fart in a spacesuit, on the other hand, is – I imagine – an olfactory gift that keeps on giving.
