DFT and coupled cluster methods were used to investigate the impact of 3d metals and ligands upon the acidity and activation of coordinated methane C-H bonds. A strong, direct relationship was established between the pK(a) of coordinated methane and the free energy barriers (Delta G double dagger) to subsequent H3C-H activation. The few outliers to this relationship indicated other salient factors (such as thermodynamic stability of the product and ligand-metal coordination type) that impacted the methane activation barrier. High variations in the activation barriers and pK(a) values were found with a range of 34.8 kcal/mol for the former and 28.6 pK(a) units for the latter. Clear trends among specific metals and ligands were also derived; metal ions such as Co-I, as well as Lewis acids and pacids, consistently yielded higher acidity for ligated methane and hence lower Delta G double dagger.