Coupled inductors are two or more inductors, or coils of wire, that are linked together by a magnetic field. This link, or coupling, allows current to flow between the inductors. This can either be done with a direct physical connection between the coils—such as through a metal core or by using a metal plate on top of both inductors—or can be done wirelessly through the magnetic field created by the current running through each coil. Coupled inductors are used for a variety of purposes, such as filtering, impedance matching, and providing energy storage.