This study investigates the fire performance of steel beams, focusing on the impact of geometric and material nonlinearities using Finite Element Analysis (FEA). The primary aim is to analyze the behavior of steel beams under fire exposure by considering the temperature-induced degradation of material properties, such as yield strength and modulus of elasticity, and how these changes influence the structural response. The research uses ABAQUS, a widely used FEA software, to model the thermal and structural responses of steel beams subjected to fire. The heat transfer analysis uses the ISO-834 fire curve, which simulates typical fire conditions, while the structural analysis incorporates the nonlinear material behavior under elevated temperatures. This includes the reduction in yield strength and stiffness, which significantly affects the load-bearing capacity of the beams at high temperatures. The influence of beam geometry, such as cross-sectional size and slenderness ratio, is studied to determine its impact on fire resistance.