Molecular modeling is the science of representing molecular structures numerically and simulating their conduct with the equations of quantum and classical physics. the usage of pc programs, polymer scientists could directly generate and obtain molecular information which includes geometries, energies, digital homes, spectroscopic residences, and bulk properties. It is a collection of (computer based) techniques for deriving, representing and manipulating the structures and reactions of molecules, and people properties that are hooked in to these three-dimensional structures. This lecture course aims to introduce in a simple way the hierarchy of computational modelling methods used nowadays as standard tools by organic chemists for searching for, rationalising and predicting structure and reactivity of organic, bio-organic and organometallic molecules. The emphasis will be on helping to develop a feel for the correct "tool" to use in the context of a typical problem in structure, activity or reactivity, by describing the limitations and strengths of each method. Molecular Modelling and Simulation has had a profound impact on process modelling through a far better understanding of the elemental physical and chemical interactions, by forming the idea for predicting thermodynamic properties of materials that are difficult to calculate using experimental procedures, and enabling the event of latest theories, models, processes, and products.