Ab initio calculations using G2 theory and other methods have been performed for the collision complexes of the metal ions Na+, Mg+, and Al+ with the molecules H-2, CO, N-2, NH3, H2O, HCN, HNC, C2H2, C2H4, c-C3H2, H2CCC, H2CCCC, and HCCCN. Binding energies, vibrational frequencies, and infrared intensities obtained from these calculations have been used to perform variational transition state theory (VTST) calculations for the corresponding radiative association reactions at temperatures pertinent to dense interstellar clouds and the outer regions of circumstellar envelopes. The calculated rate coefficients for radiative association reactions with H-2 and with the other smaller molecules of this group are slow compared with the chemical evolutionary time scale of cold interstellar clouds. For the largest and most strongly bound complexes considered, the rate of depletion of M+ by this mechanism becomes competitive with recombination of M+ with free electrons. Predicted rates for association in several systems at high pressure are in order-of-magnitude agreement with experiments, except for Mg+/H2O, which is predicted to be substantially faster than a recent experimental upper limit.