This lecture on Metal Casting compares die casting and sand mould casting in terms of cooling rate, microstructure, mechanical properties, and defects. Die casting provides fine grains, higher strength, good surface finish, and high productivity but faces issues like misruns, cold shuts, soldering, and gas defects. Sand mould casting, with slower cooling, gives coarse grains, lower strength, higher segregation, and rougher surfaces but is suitable for both small and very large castings.