This thesis details the development and validation of a Finite Element Method (FEM) transient thermal model for the Wire Arc Additive Manufacturing (WAAM) process, focusing on single-layer deposition of Stainless Steel 316L and Ti-6Al-4V alloys. The core objective was to accurately predict the thermal behavior, addressing the challenges of complex thermal history and heat accumulation that govern the final part's microstructure and mechanical properties. The model successfully implemented Goldak's Double Ellipsoidal heat source and temperature-dependent material properties, predicting realistic peak temperatures (up to 2800 ∘C) and melt pool dimensions (e.g., 6.2mm width, 3.4mm depth for SS316L) consistent with established experimental literature. The findings validated the FEM framework for predicting thermal gradients and cooling rates (150−250 ∘C/s at the surface), offering a crucial tool for optimizing WAAM process parameters and guiding future research into residual stress and microstructure modeling.