We report an in situ synthesis of graphene–metal hybrids using graphene as the buffer layer by a substrate-induced galvanic reaction. Ag nanoplates are obtained with the template effect of graphene, and their morphologies are tailored by light mediation. Our result suggests that defect sites or open edges of graphene favor binding with Ag atoms. The graphene–Ag hybrids have been used as Raman enhanced substrates for dye detection. The facile method for synthesis of graphene–metal hybrids opens up opportunities for the future development of optical, electronic and catalytic materials based on graphene and metals.