The nature of the metal-oxygen interactions and the bonding properties of oxygen sites have been explored by combining population analysis, including bond and valency indexes, with information based on the composition of molecular orbitals and the calculation of bonding energetics. Particular attention has been focused on the effects of basis sets and functionals on the correlations between the various approaches. The results obtained from population analysis have been found to be qualitatively consistent with those provided by bonding-energy approaches for basis sets of triple-zeta quality and all functionals tested. Use of smaller basis sets has had only a relatively minor effect on the bonding-energy results but has led to some significant discrepancies in the population analysis.