The electron is a subatomic particle that carries a negative electric charge. It has no known components or substructure, and therefore is believed to be an elementary particle.
If an element has more or fewer electrons than are required to balance the positive charge of the nuclei, then that element has a net electric charge. When there is an excess of electrons, the element is said to be negatively charged. When there are fewer electrons than the number of protons in nuclei, the element is said to be positively charged.
Independent electrons moving in vacuum are termed free electrons. Electrons in metals also behave as if they were free. When free electrons—both in vacuum and metals—move, they produce a net flow of charge called an electric current, which generates a magnetic field. Likewise a current can be created by a changing magnetic field.