Question

A large number of free electrons are present in metals. Why there is no current in the absence of electric field across it?

Answer 1

In a metal, large number of free electrons are found. These electrons are in constant random motion that means they are moving here and there.

Thus, current generated in one direction is cancelled out by current generated in opposite direction by these randomly moving electrons.

so, net current in a metal is zero. But under applied electric field, all electrons move in one direction resulting net current. Electric field is generated by connecting the two end of wire with two ends of a battery.