Native copper nuggets is simply a term to describe raw copper--just nuggets of the metal. These haven't been processed, melted, or used--at least to my own knowledge.
Copper, which was the first metal I worked with when starting to make jewelry, is a vibrant base metal that has a beautiful color and is the third most consumed industrial metal in the world. Copper is used for many, many things besides jewelry but you can learn more about the jewelry aspects of it here.
Metaphysically, copper is known to help balance both the physical body while amplifying and aligning the energies of any stones or crystals it's wrapped or made into something with.
Circle City Copperworks points out that copper is man's oldest metal and dates back more than 10,000 years. There was even a copper pendant discovered in what is now northern Iraq and that pendant was dated to around 8.700 B.C. During those times, copper was a symbol of wealth and there were even copper bathtubs.