Geometry, electronic structure, and bonding analysis of the terminal neutral dihalogallyl complexes of nickel, palladium, and platinum trans-[X(PMe3)(2)M(GaX2)] (M = Ni, Pd, Pt; X = Cl, Br, I) were investigated at the BP86 level of theory. The calculated geometries of platinum gallyl complexes trans-[X(PMe3)(2)Pt(GaX2)] (X = Br, I) are in excellent agreement with structurally characterized platinum complexes trans-[X(PCy3)(2)M(GaX2)]. In the gallyl complexes of nickel and palladium, the M-Ga sigma bonding orbital is slightly polarized toward the gallium atom, while in the platinum gallyl complexes, the M-Ga sigma bonding orbital is slightly polarized toward the platinum atom. It is significant to note that gallium atoms along the M-Ga sigma bonds have large p character, which is always >51% of the total AO contributions, while along the Ga-X sigma bonds, the p character varies from 72% to 73%. The short M-Ga bond distances, in spite of the significantly small M-Ga pi bonding, are due to the large s character of gallium (similar to 45-48%) along the M-Ga bonds. The calculated NPA charge distributions indicate that the metal atom carries negative charge and the Ga atom carries significantly large positive charge. The contributions of the electrostatic interaction terms, Delta E-elstat, are significantly larger in all gallyl complexes than the covalent bonding Delta E-orb term. Thus, the [M]-GaX2 bond in the studied gallyl complexes of Ni, Pd, and Pt has a greater degree of ionic character (65.7-72.5%). The pi-bonding contribution is, in all complexes, significantly smaller than the sigma bonding contribution. In the GaX2 ligands, gallium dominantly behaves as a sigma donor. The interaction energy increases in all three sets of complexes via order of Ni < Pd < Pt, and the absolute value of Delta E-Pauli, Delta E-int, and Delta E-elstat contributions to the M-Ga bonds decreases via X = Cl < Br < I in all three sets of complexes.