We presentMetal-dielectric interfaces the results of a combined experimental and theoretical investigation of linear and nonlinear light-matter interaction with metal nanolayersMetal nanolayers when excited with intense, femtosecond laser pulses. Focusing on second and third harmonic generation from gold and aluminum nanolayers and their corresponding plasmonic nanostructuresNanostructures, we highlight the roles played by bound and hot electrons. A hydrodynamic-Maxwell model that incorporates surface, bulk, and magnetic nonlinearities intrinsic to metal surfaces is implemented to explain and validate our experimental results. We uncover novel behavior of second harmonic generationSecond harmonic generation in aluminum, where resonant absorption reveals an unexpectedly dominant influence of bound electrons across the optical spectrum, suggesting that a different basic approach is required to fully explain the physics of surfaces. From another side, THGTHG in gold nanolayers has at least two main sources: interband transitionsInterband transitions (Lorentz resonancesLorentz resonances, with NL interactions governed by the bulk nonlinearity) and hot electronsHot electrons, whose relative strength is determined by temperature-dependent effective mass and only the combination of both species can predict the experimental results.