Why are most metals found in the Earth as compounds rather than as free metals?

Most metals are found as compounds because they are more stable in that form. In the Earth’s crust, metals combine with oxygen, sulfur or other elements to form oxides, sulfides or other minerals. These compounds are energetically favourable and resist oxidation or corrosion. Only very unreactive metals, such as gold, are found in their elemental form because they do not readily combine with other elements.

The answer demonstrates understanding of the chemical stability of metal compounds and the reason why extraction processes are required. It tests recall of the fact that metals are usually in compound form and application of the concept of chemical stability.