Metals all have very similar properties, many also react in the same way with other chemicals. For example they react with acids to produce hydrogen gas, and a salt. How vigorously they react can vary enormously, iron reacts only very slowly with water to produce rust whereas potassium bursts into purple flames on contact with water. This property we call reactivity, metals can be placed in a reactivity series usually from most to least reactive. Metals at the top of the list react violently releasing large amounts of energy usually as heat, the metals at the bottom may not react at all.