What is a transition metal?

Transition metals include familiar elements such as iron, copper, nickel, silver, and gold. They are often shiny, conductive, and capable of forming compounds in different oxidation states, which makes them especially versatile in chemistry. Many transition-metal compounds are colored because of how their electrons absorb light. Iron has been central to tools and infrastructure for millennia, and copper is essential in wiring and electronics. Their chemistry is vital in catalysts, magnets, pigments, and metallurgy.