Chemical bonding of the monovalent metal-doped germanium Ge2M (M belonging the groups IA and IB) clusters is investigated by using quantum chemical calculations combined with the analyses of natural atomic orbital (NAO), natural bond orbital (NBO) and natural resonance theory (NRT). All of the clusters have a ground state in isosceles triangle shape with two quasi-degenerate electronic states ( 2 A1, 2 B1). The clusters doped with metals of the group IB are more stable than those doped with the alkali metals of the group IA due to the stronger Ge-M bond of the former ones. Most clusters have the electron transfer from the dopant atoms to the dimer Ge2. This study reveals that the Ge-M bonds is very weak and highly ionic with M being alkali metals, while they are stronger and possess both ionic and covalent nature with a larger contribution of the ionic character for M being IB elements. The participation of AO-d in the Ge-M bonds of the IB elements is the reason for their larger strength and covalent character.