Unique Copper Nugget with Polished Exposed Side. Copper is one of the few metals that can occur in nature in a directly usable metallic form. This led to very early human use in several regions starting from 8000 BC. Thousands of years later, it was the first metal to be smelted from sulfide ores (5000 BC), the first metal to be cast into a shape in a mold (4000 BC), and the first metal to be purposefully alloyed with another metal, tin, to create bronze (3500 BC).