The overall approach to this thesis would be to start off by making a simple system (with the system boundaries) for steel and aluminium in an average car. The purpose of this would be to find out how one material can be used to substitute the other. The next step would involve looking into the historical stocks of steel and aluminium in cars and predict how they will be in the future. This will be done using dynamic MFA. It will be a global study of cars with a high focus on aluminium.The study will also look into the energy consumption and emissions (focusing on the climate change potential from cars). Historical and future emission scenarios will be made. Different scenarios for climate change mitigation will be tested, including light-weighting, a shift to electrical cars (Blue Map Scenario) and many other steel and aluminium related scenarios. The scenarios would be discussed and compared to results from LCA to show how the results are varying.