This paper presents an investigation into the effects of Laser Shock Peening (LSP) on the mechanical performance of metallic materials, focusing on microhardness and residual stress. In today’s rapidly evolving industrial sector, metal materials serve as the core of various mechanical equipment and infrastructure, making their performance optimization particularly crucial. Especially in fields such as aerospace, automotive manufacturing, rail transportation, and energy, metal materials must not only endure extreme temperature and pressure environments but also exhibit excellent mechanical properties, including high strength, toughness, fatigue resistance, and corrosion resistance, to ensure safe operation and extend equipment lifespan. In recent years, the rapid development of laser technology has drawn increased attention to LSP as an innovative surface modification technique. By utilizing a high-energy laser beam to induce shock waves on the surface of metallic materials, LSP offers a precise and high-speed impact treatment that significantly improves microstructure and mechanical properties. Experimental findings demonstrate a substantial increase in microhardness after LSP treatment, with notable improvements observed at considerable depths. Furthermore, LSP has a significant impact on the distribution of residual stress, particularly by introducing beneficial surface compressive stresses that enhance fatigue performance. However, the presence of deep tensile stresses poses potential challenges that may affect long-term durability. Through extensive research on various metallic materials, this study underscores the immense potential of LSP technology in enhancing the fatigue performance and mechanical properties of metals, emphasizing the importance of managing subsurface stresses alongside surface strengthening to maximize overall material performance.