That’s Heavy Melee Weapons, not Heavy Weapons.
Use Candyman’s Skill Chart to see how skills are related to actions. http://www.candyman.se/pe/skillchart/
As you can see, Heavy Weapons and Stamina aren’t used yet and Metallurgy is used in crafting.
(1) Heavy Weapons cant be skilled atm
(2) Metalurgy is a crafting skill from crafting Metal Components. Some miners believe that this skill could help finding better metal deposits like Iron, Gazz, Copper …