Sources of metal can be found in ores, which are rocks or minerals from which a metal or valuable mineral can be extracted. Ores are typically found in the Earth's crust and contain a high concentration of a certain metal. Mining is the process of extracting these ores from the ground, and then refining them to extract the metal. The most common sources of metal are copper, iron, lead, and zinc. Other metals such as gold, silver, and platinum can also be found in ores.