Soft‐x‐ray photoemission measurements of ultrahigh vacuum‐cleaved InP‐metal interfaces reveal two classes of microscopic chemical structure. Reactive metal (Al,Ni)‐InP interfaces display cation‐rich outdiffusion, atomically abrupt microstructure, and low Schottky‐barrier height (&fgr;SB), while unreactive metal (Au, Cu)‐InP interfaces exhibit anion‐rich outdiffusion, diffuse microstructure, and high &fgr;SB. For InP and other III‐V compound semiconductor‐metal junctions, chemical bond strength dominates local atomic structure and the type of electrically‐active sites produced near the interface. These features can be controlled extrinsically by Al or Ni interlayers.