The average ground-state energy of a charged spherical metal cluster with N atoms and z excessive valence electrons, i.e., with net charge Q=&ez and radius R=r s N 1ร3 , is presented in the liquid drop model (LDM) expansion E(N, z)=a v N+a s N 2ร3 +a c N 1ร3 +a 0 (z)+ a &1 (z) N &1ร3 +O(N &2ร3 ). We derive analytical expressions for the leading LDM coefficients a v , a s , a c , and, in particular, for the charge dependence of the further LDM coefficients a 0 and a &1 , using the jellium model and density functional theory in the local density approximation. We obtain for the ionization energy I(R)=W+:(e 2 รR)+O(R &2 ), with the bulk work function W=[8(+ )&8(0)]&e b , given first by Mahan and Schaich in terms of the electrostatic potential 8 and the bulk energy per electron e b , and a new analytical expression for the dimensionless coefficient :. We demonstrate that within classical theory := 1 2 but, in agreement with experimental information, : tends to t0.4 if quantum-mechanical contributions are included. In order to test and confirm our analytical expressions, we discuss the numerical results of semiclassical density variational calculations in the extended Thomas Fermi model.