Duduli

Metals are very good conductors.The high conductivity of metals is due to the presence of free electrons.These free electrons inside a metallic conductor move freely inside the metal.They continuously collide with the fixed (localized) atoms and thus behave like an electron gas.Fermi-Dirac derived an expression for the distribution of energies among electrons in the electron gas in a metal on the basis of these assumptions.

This statistics was developed by S.N. Bose for light quanta, called photons and generalised by A.Einstein to describe the energy distribution among particles, whose spin angular momenta are nh where n=0,1,2,3,..... such particles are called bosons.  wave  functions are symmetric on interchanging two bosons. The pauli exclusion principle which states that in each quantum state there cannot simultaneously be more than one particle, is not applicable to bosons, so that there is no upper limit to the number of bosons in a given quantum state.