High-power electronic components generate significant amounts of heat that must be removed in the course of normal device operations. Certain types of electronic components, such as some monolithic microwave integrated circuits and LEDs, can contain materials that are difficult to effectively bond to a heat gink in order to establish a thermal interface between the two. Device assemblies can include a heat-generating electronic component in thermal communication with a metallic heat sink via a metallic thermal interface layer. The metallic thermal interface layer is disposed between the heat-generating electronic component and the metallic heat sink. The metallic thermal interface layer is formed from a composition including a plurality of metal nanoparticles that are at least partially fused together with one another. Methods for forming a thermal interface layer include heating metal nanoparticles above their fusion temperature and subsequently cooling the liquefied metal nanoparticles to promote bonding of the electronic component.