The nanoscale metallic gaps generate the unique local electromagnetic field enhancement effect due to the strong electromagnetic coupling between closely spaced nanostructures. Besides the conventional material deposition or removal strategy, laser shock reshaping (LSR), based on the ultrahigh-strain-rate deformation of the nanometals, provides a viable process for ultrafine-gap fabrication. However, the extreme deformation behavior of nanometals during the high-speed forming process, which significantly determines the forming precision and quality, is largely unexplored. In this study, the scalable fabrication of the nanogaps was achieved using the LSR process; the extreme deformation behaviors of the nanometals were comprehensively investigated. The results indicated that the geometry of the primary structure and the LSR process will signally affect the microstructure evolution and deformation behavior of the sidewall during the LSR reshaping processes, and further affect the final geometrical morphology and optical properties of the generated nanogaps. The discovery of geometry-dependent deformation behaviors of the metallic structures is of great significance to the understanding of the mechanical deformation based nano-manufacturing processes.