The present study provides a detailed investigation of water and oxygen interactions with the Fe(100) surface using DFT calculations, in order to reveal insights into the fundamental mechanisms of iron corrosion. The results revealed that water orientations that is, H-down, Hup, and H-mix, on the Fe(100) surface, play different roles in determining interfacial properties, such as electronic structure and surface reactivity. The H-down water configuration was found to be the most stable, with stronger water-surface interactions. Moreover, analysis of water structure at applied potentials demonstrated that water adsorption becomes more pronounced at positive potentials, enhancing surface oxidation. Dissolved oxygens, another key player in corrosion, also interacted strongly with the Fe(100) surface, particularly at the hollow sites and bridge sites of the Fe(100) surface. Moreover, oxygen atoms adsorbed at bridge sites were found to facilitate water dissociation by reducing the energy barrier for O-H bond breaking, likely acting as a catalyst. This highlights the dual role of oxygen in promoting both water dissociation and iron surface oxidation, contributing to iron corrosion. In conclusion, this study sheds light on the complex interplay between water, oxygen, and the Fe(100) surface, with implications for understanding the initial stages of corrosion mechanisms at the atomic scale.