Scrap is a resource used by Torbjörn to create Armor Packs, and previously was used to upgrade his Turret. Torbjorn can hold up to 200 Scrap, and can collect 15 scrap from the pickups left behind by eliminated heroes. Scrap amount persists through deaths.
Torbjörn collects scrap through his passive, Scrap Collector. His Ultimate ability, Molten Core, used to provide him with unlimited Scrap, but this has since been reworked, as Scrap is now used exclusively for his Armor Packs, which now has no cooldown.