we get information that how metal react with water ,acid and bases.We also get to know  about there features that they are highly reactive,moderately reactive or least reactive in I am giving you activity series of metal

potassium                      k

sodium                          Na

calcium                          Ca

magnesium                   Mg

aluminium                     Al

zinc                                Zn

iron                                 Fe

hydrogen                       H

copper                            Cu

mercury                          Hg

silver                               Ag

gold                                Au

through potassium to aluminium they are highly reactive

Through zinc to copper they are moderately reactive

Through silver to gold they are least reactive.

2 1 2
We get to know the nature of reaction and the ability of a metal to react with other chemicals like acids and water. Also, we get to know if the metal will displace the other reactant in a chemical reaction. Potassium (K) to Calcium (Ca) react even with cold water and the reaction is highly vigorous. Mg to Fe react with hot water or steam and the reaction is not so vigorous but moderate. However, metal below H hardly react and are mostly inert. Cu reacts with concentrated acids only and not dilute.