An analysis of the geometries and electronic structures of a series of [L_nM(CX₃)] species (where X = H, F) is presented, on the basis of density functional theory (DFT) and the natural bonding orbital (NBO) approach. Computed geometries show that L_nM-CF3 bonds can be up to 0.1 Å shorter than the equivalent L_nM-CH₃ bonds, although the extent of this shortening varies considerably depending on the LnM fragment. Evidence for CF₃ having a higher trans influence than CH₃ is seen, but this is most apparent in systems where the L_nM-CF₃ bond is itself shorter. NBO calculations show that the computed charge at the metal center is usually slightly more negative (or less positive) in the [L_nM(CF₃)] species compared to that of its CH₃ congener. Further detailed NBO analyses on the [(H₃P)₃Rh(CX₃)] (1), trans-[(H₃P)₂Pt(Cl)(CX₃)] (2), [(OC)₅Mn(CX₃)] (3), and [Pt(H)₃(CX₃)]^2- (8) pairs indicate a significantly higher M←CX₃ σ interaction when X = F. The L_nM-CF₃ σ bond is computed to have much higher C 2s character and is also enhanced by contributions from the C-F σ* orbitals. In contrast, any M→C-F(σ*) π back-donation is relatively weak, being at most 8% of the magnitude of M←CF₃ σ interaction, while M→C-H(σ*) π back-donation is negligible in the [L_nM(CH₃)] congeners. The metal-based d orbitals are computed to be between 0.4 and 0.7 eV lower in energy in the [L_nM(CF₃)] species. Thus, CH₃/CF₃ replacement has two significant, apparently counterdirecting, effects, in that it both maintains and indeed can increase the electron density at the metal center, while at the same time causing a stabilization of the metal-based d orbitals. These effects account for the enhanced reactivity of [L_nM(CF₃)] species toward nucleophiles and form a basis for understanding the reactivity of [L_nM(CF₃)] species in the literature. Implications for the Pd-catalyzed trifluoromethylation of aryl halides ArX are discussed: in particular, the balance between Ar-CF₃ reductive elimination from [L_nPd(Ar)(CF₃)] and the propensity of this species to undergo transmetalation (and hence catalyst deactivation) in the presence of [L_nPd(Ar)(X)] species.