system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does copper jewelry keep it's shine if you wear it?

Copper goes dark if in air contact. But if you wear a copper ring or a bracelet it remains quite shiny! Why does that happen? The outer part of the ring\bracelet isn't even in direct contact with the skin.

SCIENCE I AM RELYING ON YOU.
gpt
Copper is pretty dang soft as metals go. Soft enough that just the simple action of wearing it, having it rubbing against clothing and your skin is enough to keep it nicely buffed. Rings will rotate on the finger, and will rub against your other fingers, or against your clothing way more than you might expect. That's more than enough to keep the corrosion at bay. 

You see the same effect with silver rings - if they're worn they stay fairly decent looking. If you store it away in a drawer and go have a look at in a years' time, you'll find it's got a fairly heavy patina on it. 

Gold doesn't do this to anything like the same degree because it's so unreactive. Gold will happily stay shiny when at the bottom of the ocean or buried. This is one of the properties that contributed to its perceived value.