A copper wire is a lattice of copper ions in a sea of free electrons. The electrons fly about at random at over 1,000 km/s, bouncing off ions and imperfections, and with no voltage they go nowhere on average. A voltage adds a small, steady push in one direction, so each electron's zigzag path creeps along the wire: that slow creep is the current. Here the drift is shown thousands of times faster than it really is. In a real wire it is a fraction of a millimetre per second.