Close to Metal

Close to metal means that something is very close to where it's located in the physical world, like a metal object. Instead of being a long way away, it is close to the metal. In this case, close to metal might mean that the idea, product, or system is very close to the hardware that makes it work instead of being in the cloud or remote. Put simply, close to metal means that something is close to its physical source, instead of being far away.