High-luminosity and high-energy-resolution photoemission spectroscopy can provide direct observation of the spectral density of metal-induced states throughout the whole band gap, even at extremely low metal deposition. We present a study of the density of states of a two-dimensional electron gas induced in the InAs(110) conduction band by deposition of caesium, antimony and silver adatoms. We follow the density of states redistribution between the two-dimensional electron-gas channel and the appearance of metal-induced gap states.