Metal and Mind Viruses
I think that anyone who designs things should form metal by hand at least once in their lives. Reshaping a normally unyielding material as if it were a piece of plasticine gives you a newfound respect for your own capabilities. At the same time, as you quench your piece and it sets into the shape you gave it, you intuit the fact that anything you cast, coax or force out of metal is going to be around for much longer than you are.
Making something with metal means that you've done something which will endure for hundreds or even thousands of years. In a way, that's not exactly unusual. Today even our choices as designers will have far-flung and enduring legacies, and not all of them will be pleasant. But you don't normally get to see your legacy taking shape and have such obvious and direct agency over its form, and you don't normally get to hold it in your hands. The feeling that you get from doing so won't be easy to forget.