Exciton-surface plasmon coupling is at the heart of the most elementary light-matter interactions and is a result of not only an intrinsic property of the emitter but that of emitter-environment interaction. Thus, change of electromagnetic environment, as in case of metallic nanoplasmonic structures and an emitter, significantly modifies the near field light-matter interaction, which leads to energy transfer in the form of exciton between metallic nanostructure and the emitter. However, this mechanism remains largely unexplored. Here, we developed and applied semi-classical electrodynamics theory and modeling techniques to analyze the energy transfer mechanism in exciton-surface plasmon coupling. The quantum efficiency of an emitter was investigated as a function of the location of the emitter with respect to nanoparticles and their assembles whose local plasmonic field modified by forming complex coupling modes as well as the local dielectric environment. The research provided a theoretical insight into fundamental science of nanophotonics and shed light on unprecedented applications in wide range fields such as ultra-low power lasers, quantum information processing, photovoltaics, photocatalysis, and chemical sensing.