Optimum design is the search for better solutions which minimize the cost function and fulfil the design constraints. The search for optimum is a natural demand of thinking people. Optimum design is a structural synthesis which adds the aspects of economy to design constraints. The three main phases of the structural synthesis are: analytical phase, mathematical phase and phase of evaluation by the engineer. Optimum design should play an important role in the education as well, since it can give a wide view necessary for engineers. The optimum design of metal structures is like a slimming cure: The best way to decrease the weight of structures is to decrease the plate thicknesses. Optimum designers are always optimistic, since they hope to find suitable optima. The chapter also presents an overview of the key concepts discussed in this book.