Wikipedia also says this about his shield.

Quote Originally Posted by Wikipedia
Captain America uses several shields throughout his history, the most recognizable of which is an indestructible discus-shaped shield made from a fusion of vibranium with an experimental steel alloy (not adamantium-vibranium as sometimes erroneously stated).
In a fight, I think Captain America would win. Unless Cloud could find a way to bypass the shield, which would be unlikely.