Surface-enhanced Raman Spectroscopy (SERS), attains its high sensitivity with a large signal amplification due to the usage of noble-metal nanoparticles as substrates. This surpasses the underachieving reactivity of Raman Spectroscopy and can be further used in the detection of various analytes and for molecular recognition in the fields of food processing, biosensing along with ecological conservation. However, due to SERS substrates being non-reusable, and extremely valuable and expensive, studies are being undertaken on feasible and cost-effective SERS substrates, consisting of noble-metal hybrid nanostructures. While ensuring reusability, with an evolved morphology and chemical profile, the hybrid nanostructures help improve SERS activity. This chapter reviews the noble-metal nanostructures, consisting of silver (Ag), and gold (Au), in the form of monolayers, nanorods, nanotubes, and nanoclusters. The hybrid structures are constructed with other noble-metal nanostructures, as well as transmission metal oxides (TMOs), transition metal dichalcogenides (TMDCs) and other nanomaterials, as substrates, while discussing their synthesis techniques, characterization techniques, along with the mechanism for SERS, followed by the substrate. It also studies the impact of dielectric environment, change in nanostructure along with method of synthesis and assembly of the substrate on SERS activity.