Metal particles supported by carbon materials are important for various technologies yet not well understood. Here, we report on the use of well-defined colloidal graphene quantum dots as a model system for the carbon materials to study metal-carbon interaction. In the case of palladium, our studies show high affinity between the metal nanoparticles with the graphene. IR spectroscopy reveals covalent nature of the interaction between the two, which had been predicted by theoretical calculations yet never directly proven before.