To add to that, terms like Bronze age refer to different times in different locations depending on when bronze began being used. It would refer to an earlier time in the near East than it would in Scandinavia(3300 BC vs 1700 BC). It is not as relevant in the Americas as metallurgy didn't even appear to exist in pre-Columbian North America. There was some minor use of bronze in certain South American cultures but it doesn't seem to have been extensive enough to define a time period.