The elements don't cancel each other, instead they become something different. It becomes mixed or something else depending on the number of different elements put together. There is fire, ice, lightning, shadow, light, and more.
I find that mixing isn't usually as good as putting a ton of a single element on there, unless of course you have a recipe. If you don't have the lightning element yet you probably don't have enough of a single element to bring it up to a different name so mixed is probably better. Try on your own still, you will probably find something i didn't.
I really love the element mechanic. Mixing isn't the only thing that matters since adding enough stone and only stone can change it to obsidion, etc. I did screw myself a few times though. Once I loaded up the goblins outside the town with all my iron so I would remember where I put it while I was in the forest. I forgot about it and they kicked my ass on my way back to town.