The chemical bonding, extent, and evolution of metal‐oxide semiconductor interface regions have been probed with soft‐x‐ray photoemission spectroscopy following room‐temperature, in situ metallization. We identify strong atomic rearrangement and charge transfer at metal‐SiO2 interfaces. The quantitatively different processes found for Au and Al suggest new structural models. For Al‐SiO2, Al first clusters about each surface O and then grows Al2O3 by reducing SiOx (X < 2) and leaving excess Si at the interface. In contrast, Au forms islands on SiO2 with evidence of Au–Si bonding, causing an SiOx layer beneath the contact.