I think copper is the best thermal conductor because when heat is applied to one area of a metal, the molecules within that area will receive thermal energy and start to vibrate more quickly, when they vibrate, the particles bombard more with neighbouring particles and transfer over some of their energy, which is thermal energy and then the metal starts heating up. Copper is made from a lattice of ions with free electrons.The ions are vibrating and the electrons can move through the copper.
