Question

Why HNO3 does not react any metals except magnesium and manganese to liberate hydrogen gas?

Answer 1

Nitric acid(HNO3) is a strong oxidising agent.
The Hydrogen gas produced during its reaction with metal gets oxidised to H2O, hence no hydrogen gas is produced.
Instead it evolves nitric oxides such as  NO2,NO etc.

For Eg:
Cu(s) + 4HNO3(aq)--->Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l