Clearly superior to metal Depending on the application, sapphire, ceramics, and other hard materials have substantial benefits over metals. In compression, the materials we manufacture are tougher and stronger than most metals. They won't break or bend under pressure. In tension, their stiffness makes them ideal for transmitting force without loss while maintaining precise tolerances. They're not going to stretch or deform under load. Finally, they're not going to rust. Not even when exposed to water or acid. The best option for those applications is an alloy that contains some degree of steel in its composition. However, steel is a relatively soft material so it's good for cutting tools too. The next option is ceramic. This is usually made up of several different types of ceramic materials that are bonded together to create one solid piece. While ceramic is extremely hard, it can be brittle meaning it will break if you apply stress to it. That's why tools made from this material need to be carefully designed and manufactured. Last but not least there's sapphire. Sapphire is the hardest natural substance known to man! It can withstand temperatures up to 2000 degrees Fahrenheit (1093 degrees Celsius) before changing color or becoming deformed. So, yeah, all kinds of things can be used instead of metal.