The effect on the metal-ligand bond strength is studied of substituting a hydrogen in a methyl ligand by groups with lone-pairs. In particular, the presence of eta(2) coordination is investigated. Complexes from the entire second row of the transition metals from yttrium to palladium are discussed. Several surprising results are obtained. For example, the metal-ligand bond in MCl-CH2(NH2) is for the metals to the right up to 25 kcal/mol more stable than the metal-ligand bond in MCl-CH3. Another surprising result is that for the metals to the left the corresponding lone-pair stabilization is much smaller, only 10 kcal/mol. Also, the lone-pair stabilization for the metals to the right is dramatically dependent on the presence of halide ligands. Most of the results are explained by the appearance of an electronic resonance configuration which introduces both donation back-donation bonding between the metal and the ligand and also pi-bonding on the ligand. This resonance picture is quite different from the one used to explain the effects of eta(2) coordination for acyl complexes to the left. The importance of the energies of the lone-pairs and the number of lone-pairs is also stressed in a comparison of amino, hydroxyl, and fluorine substituents.