Explain why noble metals like gold and platinum are found in a free state in nature, while most other metals are found in combined states.

Noble metals like gold and platinum are at the very bottom of the reactivity series. They are highly unreactive and do not readily combine with other elements like oxygen, water, or acids present in the environment. Due to their low reactivity, they exist as free elements (native state) in the Earth's crust. Most other metals are more reactive and readily form compounds with other elements, hence found in combined states as ores.