Ores are naturally occurring rocks that contain metal or metal compounds in sufficient amounts to make it worthwhile extracting them.
Iron ore is used to make iron and steel. Copper is easily extracted, but ores rich in copper are becoming more difficult to find. Aluminium and titanium are metals with useful properties, but they are expensive to extract. Most everyday metals are mixtures called alloys.
The Earth's crust contains metals and metal compounds such as gold, iron oxide and aluminium oxide, but these are often mixed with other substances when found in the Earth. To be useful, the metals have to be extracted from whatever they are mixed with. Metal ore is a rock containing a metal, or a metal compound, in a high enough concentration to make it economic to extract the metal.
The method used to extract metals from the ore in which they are found depends on their reactivity. For example, reactive metals such as aluminium are extracted by electrolysis, while a less-reactive metal such as iron may be extracted by reduction with carbon or carbon monoxide. The method of extraction of a metal from its ore depends on the metal's position in the reactivity series: