here in an conductor the binding energy will be soo less tht even at room temp. also the electron will leave the nucleas and will move freely in the conductor, where as the nucleus are held together by nuclear forces and they r the only +ve charge in the conductor so if they will start moving thn we will find tht whole matter is moving as if the nuclear forces r weakened and the conductor has melted............

so as far as i think +ve charges dnt move so only -ve charges contribute to drift velocity...........