Single-molecule magnets (SMMs) are molecules that show magnetic properties at the molecular level. With the world evolving toward the miniaturization of electronic devices, single-molecule magnets are showing potential in spin-based computing and information storage, etc. They have drawn attention in recent years with the quest to achieve higher magnetic anisotropies. Along with f-series complexes, transition-metal-based systems with unquenched angular momentum are new-found in the field of SMMs. Both SOC and ligand environment, i.e. crystal field control magnetic anisotropy, which further rules to govern the barrier height to magnetization reversal are important. A comprehensive understanding of the electronic structure, using first principle methods like DFT and other ab initio multireference methods of CASSCF/NEVPT2, is crucial while looking for an efficient SMM. We study various spin-relaxation pathways and spin-phonon coupling mechanisms to explore and enhance the magnetic anisotropy of SMMs. Besides, the magneto-structural correlations showing the possibility to fine-tune the magnetic anisotropy via modulation in the symmetry of the system are studied in depth to unravel plausible SMMs.