Perhaps the mysterious part is how current works. In the wire, free electrons push on each other kind of like cars on a road. If there is a blockage as in an open switch or an opposing voltage push back at the other end, the electrons near that end are stopped like cars at a red light or crashing into stationary vehicles. The stationary electrons push back on those behind via their electric force (like charges repell), bringing the movement of electrons to a stop in the whole length of wire just as happens to cars on a road.
