The Earth's crust contains many metals, but most of them are not found as pure metal. Most metals are extracted from ores. An ore is a rock that contains enough of a metal compound to make it worth extracting the metal.
Reactive metals have combined with other elements over millions of years, so they are found as compounds. Iron, for example, is found combined with oxygen as iron oxide.
Unreactive metals such as gold do not easily react with other substances. They are found in the Earth's crust as the uncombined element, so they can be collected without a chemical reaction.