Over the past two decades the science and engineering oforganic semiconducting materials have improved very rapidly, leading to the optimization and demonstration of a range of organic-based solid-state devices. A key to design high performance molecular electronic device is the understanding of function and characteristics of organic materials while they are in-contact with metal. Hence, a systematic theoretical investigation 210on the structure and electronic properties of the organic molecule/metal interfaces is required to find the ideal material sets with improved properties for use in next generation organic electronic devices. Finding the adsorption geometry of organic molecule on the metal surface and their electronic properties is a challenging task while optimizing the new electronic devices. In this chapter, the first principle based theoretical methods to predict the stable adsorption geometry of organic molecule on the metal surface is discussed. The electronic properties, such as change in work function, density of states (DOS), population analysis, frontier molecular orbital analysis and Schottky barrier height (SBH) are used to characterize the charge transport properties of organic molecule/metal interface. The interface between pentacene organic molecule and Pd(100) surface and the electronic properties are discussed.