This thesis presents a new metric-based Life-cycle Assessment (LCA) method for assessing the sustainability performance of metallic automotive components. The unique feature of this research work include the development and use of a metrics-based product sustainability index (ProdSI) methodology by considering the total life-cycle approach and the triple bottom line (TBL) with the 6R methodology. It has been shown that the manufactured product’s sustainability performance can be comprehensively assessed using this new methodology. The major focus of this research is the integration of the 6R activities (Reduce, Reuse, Recycle, Recover, Redesign and Remanufacture). Four life-cycle stages of the product, with various end-of-life (EOL) product scenarios, are modeled and analyzed. These scenarios include: reuse, remanufacturing, and recycling the products at EOL. Furthermore, a new mathematical model is developed and presented to determine the optimum percentage mix for various product EOL strategic options. By using the 6R methodology, the overall product sustainability was significantly improved. This improvement was quantitatively assessed by computing the ProdSI score. Ultimately, this research shows that a closed-loop material flow can be achieved.