What we know as the mirroring shiny trim that makes bikes and cars look incredible is actually a pretty interesting element called Chromium, or as most people know it: Chrome.
Not only is it used because of its great aesthetic quality, it is also very durable and can be used for it's strengthening properties in alloys.
When you add Chromium to iron you can create a kind of stainless steel alloy, which is found in everything from bridges, to cars to wristwatches.
The chrome trim you see on cars is probably chrome plating, where a very thin layer of chromium is electroplated onto layers of metal or plastic. It's usually very thin, but will be thicker in areas that are effected by high temperatures or more easily damaged.
This video shows a new method of spraying on chrome plating:
