Changes in the preferential sites of electrophilic, nucleophilic, and radical attacks on the pristine C-60 surface with endohedral doping using 3d transition metal atoms were studied via two useful reactivity indices, namely the Fukui functions and the molecular electrostatic potential. Both of these were calculated at the density functional BPW91 level of theory with the DNP basis set. Our results clearly show changes in the preferential reactivity sites on the fullerene surface when it is doped with Mn, Fe, Co, or Ni atoms, whereas there are no significant changes in the preferential reactivity sites on the C-60 surface upon endohedral doping with Cu and Zn atoms. Electron affinities (E-A), ionization potentials (I-p), and HOMO-LUMO gaps (E-g) were also calculated to complete the study of the endofullerene's surface reactivity. These findings provide insight into endofullerene functionalization, an important issue in their application.