Transient-liquid-phase (TLP) joining and liquid-film-assisted joining (LFAJ) exploit thin metallic films that melt at relatively low temperatures as part of a multilayer, multimaterial interlayer to enable joining at reduced temperatures. These methods are attractive for assemblies that include temperature-sensitive components, however, unlike conventional low-temperature joining methods, they also offer the potential for service at temperatures approaching or even exceeding the original joining temperature. In successful TLP joining and LFAJ, the wetting behavior of the liquid plays a critical role. In TLP joining, the liquid ultimately disappears during joining due to interdiffusion and chemical homogenization. In contrast, in LFAJ the liquid persists at the joining temperature, provides a high-diffusivity transport path that accelerates joint formation, and ultimately undergoes a morphological transition that disrupts the initially continuous film. The resulting isolated liquid droplets solidify on cooling. Current studies of these joining methods are described, and promising future directions are indicated.