Metal–metal-oxide interfaces (MMOIs) are becoming important due to their fundamental aspects and applications. In catalysis, studying the interfaces in terms of chemical composition and microstructure/nanostructure helps in understanding the chemical processes, reaction, and mechanism at the surfaces. As a result, the conversion, selectivity, and stability of the catalysts can be enhanced. Besides, it diversifies the synthetic strategies for the design of innovative and new catalysts for industrial reactions. Amongst various important reactions, carbon monoxide oxidation and hydrogen generation from ammonia borane hydrolysis are important considering the environmental issues. Here, we present the stability of metal-supported catalysts from thermodynamics followed by general synthesis strategies for finely dispersed metal-supported oxide systems and a few specific examples related to the already mentioned two reactions. Characterizing the MMOIs is a key feature that has been discussed with emphasis on the data obtained post synthesis and in situ catalytic reactions. Following is the discussion on the effect of structural and composition changes on the reactions. Finally, we highlighted the importance of single atom and single cluster catalysis and operando techniques.