Efforts to develop an attractive biocatalyst with new chemical reactivity and selectivity indicate that promising strategies involve the construction of artificial metalloenzymes generated by incorporation of a metal-containing moiety into a protein scaffold. In this article, we present three recent results focusing on the modification of proteins with artificial metal complexes. First, an artificial hydrogenase model containing a synthetic diiron carbonyl cluster, (µ-S₂)[Fe^I(CO)₃]₂, held by a native cysteine-containing motif in the cytochrome c protein is described. The diiron carbonyl core anchored by coordination within the protein matrix works well as a catalyst for H₂ evolution. Second, a hybrid catalyst containing a rhodium complex with a maleimide moiety at the peripheral position of the cyclopendiene ligand is described. The rhodium complex was inserted into a β-barrel protein scaffold of a mutant of aponitrobindin via a covalent linkage. The hybrid protein acts as a polymerization catalyst and preferentially yields trans-poly(phenylacetylene)(PPA). Finally, an artificial hemoprotein containing an iron porphycene, a structural isomer of hemin, within a heme pocket, is reported. The reconstituted horseradish peroxidase catalyzes the H₂O₂-dependent oxidation of thioanisole, of which the initial rate is 12-fold faster than that observed for native myoglobin.