The cluster compounds KNa3In9 [K2Na6(In-12)(In)(6)] and Na2In [(Na)(8)(In-4)] which contain In-12 icosahedra interbridged by 4-bonded In atoms and isolated In-4 tetrahedra, respectively, both have classical closed-shell electronic configurations but show metallic transport properties. These contrasts have been studied by means of first-principles density functional methods (LMTO-ASA). Several bands cross the Fermi level in both compounds, consistent with their metallic properties. In KNa3In9, the metal atom framework alone is sufficient to generate a metallic characteristic. The alkali-metal s and indium p orbitals mix considerably in both phases, providing for substantial covalent contributions to their stabilities as well as bands crossing E-f. The participation of Na atoms in the 3D bonding networks is more striking in cation-richer Na2In than in KNa3In9.