A series of Cu(II), Ni(II), Co(II), Mn(II), and Zn(II) complexes have been synthesized from the schiff base ligand L. The schiff base ligand [(4-oxo-4H-chromen-3-yl) methylene] benzohydrazide (L) has been synthesized by the reaction between chromone-3-carbaldehyde and benzoyl hydrazine. The nature of bonding and geometry of the transition metal complexes as well as schiff base ligand L have been deduced from elemental analysis, FT-IR, UV-Vis, 1HNMR, ESR spectral studies, mass, thermal (TGA and DTA) analysis, magnetic susceptibility, and molar conductance measurements. Cu(II), Ni(II), Co(II), and Mn(II) metal ions are forming 1:2 (M:L) complexes, Zn(II) is forming 1:1 (M:L) complex. Based on elemental, conductance and spectral studies, six-coordinated geometry was assigned for Cu(II), Ni(II), Co(II), Mn(II), and Zn(II) complexes. The complexes are 1:2 electrolytes in DMSO except zinc complex, which is neutral in DMSO. The ligand L acts as tridentate and coordinates through nitrogen atom of azomethine group, oxygen atom of keto group of γ-pyrone ring and oxygen atom of hydrazoic group of benzoyl hydrazine. The 3D molecular modeling and energies of all the compounds are furnished. The biological activity of the ligand and its complexes have been studied on the four bacteria E. coli, Edwardella, Pseudomonas, and B. subtilis and two fungi pencillium and tricoderma by well disc and fusion method and found that the metal chelates are more active than the free schiff base ligand.