The document discusses the reactivity series, which ranks metals based on their reactivity level from most reactive to least reactive. The most reactive metals, such as potassium and sodium, readily lose electrons during chemical reactions. Less reactive metals like copper and silver are slower to lose electrons. The least reactive metal, gold, does not readily react with substances like oxygen, water, or acids. The reactivity series can be used to determine the nature of metals and predict displacement and acid-base reactions.