By means of density functional theory methods together with statistical thermodynamic analysis, the C82 monometallofullerenes including special heterogeneous triangular clusters were theoretically probed for the first time. Despite having analogous structures, the YCN@C82 and TbCN@C82 series exhibit dissimilar thermodynamic stabilities, which lead to different components of experimental products. Significant relationship between the thermodynamic stabilities and geometry structures of C82 metallofullerenes is disclosed. Studies of the electronic configurations of MCN@C82 species not only explain their redox potentials but also recover complicated interaction mechanisms within them. In addition, predictions of the optical spectra of observed MCN@C82 species coincide with experimental detections well, indicating that simulations for other structures will be helpful for future characterization of these cyanoclusterfullerenes.