Wow, I’ve always thought of this as pure magic but here’s the reasons behind the non-contact
When an alternating electric current is passed through a coil, the coil creates a magnetic field. The magnetic lines of flux cut through the air around the coil. If a ferrous material, such a solid bar of iron is inserted into this coil, certain effects known as eddy currents are induced to flow in the metal bar. This causes localised heating, and ultimately heats up the metal bar.
In an induction heater, the coil is known as the ‘work coil’.