Sting is Frodo’s sword, which he inherited from Bilbo. It glows blue when Orcs are nearby, which is mighty useful, but Sting is more than just an alarm system. It also provides a link between Frodo, Bilbo, and the much larger, multi-Age wars between good and evil in Middle-earth. Like Sting, the Ring is also a relic of these wars, but it is (obviously) a thing of evil. Sting represents the opposite: the heroic greatness of those battles, in which good Elves fought Orcs many years before Frodo came onto the scene. While Frodo may be a small Hobbit in the middle of grand doings in the world, he is as vital a part of that struggle against Evil as any ancient Elven hero.