Drude Model is a model in which the free electrons in a metal are treated like a classical ideal gas with a Maxwell-Boltzmann distribution of kinetic energies, with an average thermal energy < E > = (3/2)kT.
The essential idea of Drude’s free electron model is that each atom in a metal loses its valence electrons and becomes a positively charged ion. These ions form a fairly rigid lattice. The free electrons lost by the ions are free to wander throughout the body of the metal but are confined within the metal by the attractive forces of the positively charged ions.
The Drude model does have its limitations such as its failure to correctly account for the temperature dependence of resisitivity in metals, but it gives a good enough classical description of electrical conduction in metals which leads to Ohm’s law and shows that resistivity in a metal can be explained by the motion of its free electrons.