The molecular design and development of artificial metalloproteins formed by the complexation of metal complexes with proteins have become a fascinating topic in bionanotechnology and biomaterials in recent years, as the functions of various metal complexes can be achieved within the specific environment of proteins. This article focuses on recent progress in constructing artificial metalloproteins using cage proteins and protein crystals as molecular templates. These templates control the functions of metal complexes and capture their intermediate structures. Firstly, the synthesis of artificial metalloenzymes by immobilizing metal complexes on the cage protein, ferritin, is presented, and the direct observation method of the metal cluster formation process is demonstrated by X-ray crystallography. Next, the synthesis of solid catalysts by immobilizing metal complexes in the solvent channels of protein crystals, which are solid protein assemblies, is described. A new method for capturing nanosecond to microsecond scale intermediate structures of chemical reactions of artificial metalloproteins in real-time using the Time-Resolved Serial Femtosecond X-ray crystallography (TR-SFX) method is presented. Real-space structure determination using this method enables a new approach to visualize reactions at the atomic level of small molecules. In the future, the design of artificial metalloenzymes with precise reaction mechanisms may be facilitated, promoting the design, control, and development of innovative reactions.