SOKKA IS A METALCRAFTER!
Ok so Alera/Carna are on the other side of the world to ATLA. The alerans have crafting & the ATLAns have bending. They only have firecrafting, watercrafting, windcrafting, & earthcrafting though. Their metalbending is part of earthbending, but NOT EVERY EARTHBENDER CAN METALCRAFT! Plantbending? Well that could be woodcrafting instead of just bending the water in the plants.
Now just look at Sokka. ATLAns haven’t found a metalcrafting or plantcrafting animal yet. They had dragons, badgermoles, lion-turtles, etc, but nothing for metal or plants (except one rando in a swamp). But what if they don’t even realize they have crafting?
Sokka becomes a master swordsman & he had a boomerang that always comes back. He isn’t necessarily great with pain (at least at the beginning), but later on (when he hones his metalcrafting through learning swordistry) his pain tolerance improves. Metalcrafting.
Sokka is a metalcrafter/metalbender.