If you have an old bronze sculpture with a surface that has oxidized and turned green or brown, that coating is called a patina. A patina can appear on anything made of metal.
A patina can also be the shiny surface on wooden furniture that you get after years and years of polishing. You can also use the word in a metaphorical sense, to describe somebody who has acquired some surface character that doesn't go very deep — like the tycoon who has a patina of sophistication but only pretends to be interested in art and literature.
