How does the current flow in a wire?

Electric current is the flow of electrons in a metal wire when a cell or battery is applied across its ends. A metal wire has a plenty of free electrons in it.(i) When the metal wire has not been connected to a source of electricity like a cell or a battery, the electrons present in it move at random in all directions between the atoms of the metal wire.
(ii) When a source of electricity like a cell or a battery is connected between the ends of the metal wire, the electric force acts on the electrons present in the wire. Since the electrons are negatively charged, they start moving from negative end to the positive end of the wire. This flow of electrons constitutes the electric current in the wire.