This study shows that three molecular descriptors can be used to establish satisfactory linear free-energy relationships (LFER) allowing the quantitative modeling of essential reactions of metal ions in aquatic and surface systems. Namely, the Me-O bond length (RMe-O), the water-binding energy (DeltaE(WB)) of morrohydrated metal ions (Me(H2O)(z+)), and the lowest unoccupied molecular orbital energy of metal ions (LUMOMez+), calculated with the nonlocal density functional method can serve as the three governing parameters in the present LFER. The feasibility of the LFER in evaluating the thermodynamic constants of the deprotonation, precipitation, complexation, solvation, diffusion, adsorption, and cation-exchange reactions of aqueous metal ions is also documented. This approach can be quite useful in universally elucidating the interrelationship among various chemical reactions of metal ions in aquatic and surface systems.