We firstly compare the electric and magnetic polarizabilities of a spherical nanoparticle. We then calculate the electromagnetic heat transfer between a metallic particle and a semi-infinite substrate. We show that the power absorbed by the particle in the near field is due to the magnetic interaction. We then calculate the energy transfer between two metallic nanoparticles and compare the heat dissipated by Joule effect and eddy currents. We find that the heat dissipated due to the magnetic fields is the leading contribution to the heat power. Both calculations show that a number of near-field effects involving metallic particles are affected by the fluctuating magnetic thermal fields.