There are usually four ways to heat metal with electric energy:
Heat in a resistance furnace. The metal is installed into the furnace, the current flows through the heating element to generate heat, and the temperature of the furnace is increased by radiation and convection, so as to heat the metal.
Contact method. The current flows directly through the metal from the power supply through the contact, causing the metal to heat.
Put the metal into the electrolyte with certain chemical composition, and connect one pole of the DC power supply to the electrolyte and the other pole to the metal to be heated. In this case, the heat is separated out through the boundary between the metal and the electrolyte.
Induction heating. Using electromagnetic induction, the current is excited in the metal to heat the metal. In this case, there is no conductor connection between the induction coil and the heated metal, which needs to be separated by a certain distance.