- Reactivity of metals with water varies. Some react with cold water (e.g., alkali metals), some with hot water/steam (e.g., Mg, Al, Fe), and some react very slowly or not at all (e.g., noble metals, Pb). - Passivation is the formation of a protective layer of oxide or hydroxide on the metal surface that prevents further reaction. Aluminium and Lead are prone to passivation. - Iron rusts, which is a reaction involving water and oxygen. Magnesium reacts with hot water and steam. Aluminium reacts with boiling water and steam, and forms a passive layer at room temperature.