Cs, Ag, and Zn behave in a different way when deposited on surfaces of ultrathin (15-20 Angstrom) films of alumina. In the case of Cs/Al2O3, the alkali atoms wet the oxide, forming strong chemisorption bonds. At small coverages of Cs, desorption of the alkali occurred between 600 and 1000 K. As the amount of Cs deposited increased, there was a reduction in the Cs desorption temperature to similar to 350 K. This broad range of desorption temperatures reflects a continuous decrease in the Cs adsorption energy from 63 to 18 kcal/mol with increasing Cs coverage. The deposition of small amounts of Cs induced large (0.9-1.1 eV) positive shifts in the binding energies of the O KVV, O 1s, and Al 2p features of the alumina films. This is consistent with a transfer of electrons from Cs into surface states of alumina that produces a transformation similar to a change from p-type to n-type semiconductors, AE and Zn do not wet the surface of alumina well and form three-dimensional clusters or particles. In these systems, the activation energies for desorption of the admetal increase with cluster size (20 kcal/mol for Ag, 10 kcal/mol for Zn). The deposition of Ag and Zn induces only minor perturbations in the electronic properties of alumina. Small silver clusters supported on alumina exhibit an incompletely developed metallic band structure. The differences in the behavior of the Cs/Al2O3 and Ag/Al2O3 or Zn/Al2O3 systems are explained in terms of variations in the surface free energy of the admetals and in the nature of the admetal-oxide bonds.