The Gun Mettle Update was a major update that introduced weapon skins, 4 new maps, and 3 new taunts. It also introduced the ability to pick up weapons from the ground from fallen players, as well the Gun Mettle Campaign, a three-month event allowing players to complete skill-based contract challenges to unlock one-of-a-kind weapons and exclusive weapon cases. To participate in the Gun Mettle Campaign, players had to obtain the Gun Mettle Campaign Pass, which was available for purchase in the Mann Co. Store.

Additional content was further added in the August 27, 2015 Patch with the introduction of the Gun Mettle Cosmetic Case.