Gome is basically the rarest Golden Metal Slime you could ever encounter—one of a kind. He's Dai's oldest friend, having been there since way back when Dai was just a kid wishing for companionship. Throughout the series, Gome keeps pulling off these small miracles that end up helping Dai and the group in crucial moments.
The big twist comes later: Gome isn't actually just some random slime. He's a divine wish-granting artifact created by god himself, specifically designed to answer the prayers of people with pure hearts. When Dai was lonely and desperate for a friend, Gome answered that wish by taking on the form of a slime. Because of this origin, he earned the title "Tear of a God"—basically a physical manifestation of divine compassion.
Content compiled by AnimeList.moe from publicly available sources.