Naturally my mind turned to the chemistry that must be involved, and before I knew it, I was thinking about rusting.
Electricity is really the movement of electrons.
Batteries store electricity using at least two different chemicals. When the key starts the car, electrons leave one chemical and are allowed to flow out of the battery, through the car, and then into the other side of the battery and into another chemical. The same thing can occur in nature when two chemicals come into contact with one another. Usually this happens when two different metals are put together, although it can happen with just one piece of metal if water and oxygen are present. I know the idea of natural batteries all around us sounds kind of strange, but read on.