In nature, metals are usually found in compounds (usually combined with oxygen or sulphur). These compounds are mixed up in rocks or minerals called ores.
Copper is an unreactive metal - it reacts only slowly with the atmosphere. This means that huge lumps of copper metal are found buried in the ground as nuggets. This is called native copper. The largest nugget of native copper ever found came from Minnesota, USA and weighed over 400 tonnes. Native copper isn't mined because there is so little of it. Therefore it is of little commercial importance.
