The density functional theory simulations analyzed the structural, electronic properties, and hydrogen storage capacities of functionalized Ni and Pd on SiC, GeC, and SnC nanotubes. The functionalized Ni@MCNT (M=Si, Ge, and Sn) attaches up to five, six, and four H2 with adsorption energies (∆Eads) of (-0.210, -0.213, and -0.224 eV) and desorption temperature, Td of 475, 445, and 386 K, with storage capacities of 9.53, 7.78 and 4.08 wt%. In comparison, the functionalized Pd@MCNT attaches up to four, four, and three H2 with ∆Eads of (-0.200, -0.223, and -0.259 eV) and desorption temperatures of 392, 377, and 413 K with storage capacities of 5.22, 4.05 and 2.49 wt%. The irreversible 1H2/TM@MCNT (TM= Pd and Ni) and reversible 2H2/TM@MCNT interactions in hydrogen storage are characterized according to Density of States, Partial Density of States , hyperpolarizabilities, (infrared & Raman spectroscopy), and Gibbs free energy (∆G). non-covalent interaction (NCI), and quantum theory of atoms in molecules (QTAIM) were considered. These results suggest that TM doped on SiCNT, GeCNT, and SnCNT should be an excellent choice for reversible H2 storage