Tom Bombadil is a jovial being who reigns over the Old Forest, located just outside the Shire. While he is depicted as a comical figure who is prone to bursting out in song, he is also extremely old, possibly immortal, and has immense power over the natural world that he protects. Frodo, Sam, Pippin, and Merry encounter Tom and his wife Goldberry shortly after they leave the Shire. Interestingly, while the Ring does not appear to have any power over Tom, he does not involve himself in the fight against Sauron and his forces. Tolkien implies that this is because Tom is unconcerned with the ways of the world outside of his forest.
Tom Bombadil is the first entity that Frodo encounters on his journey. He rescues Frodo, Sam, Pippin, and Merry from the clutches of Old Man Willow and the barrow-wights and he also provides the Hobbits with food and shelter. This is significant for two key reasons. One, the Hobbits’ encounter with Tom Bombadil and the Old Forest is the first step of their adventure and it marks that they have left the comforts of home behind to embrace a complete unknown. And two, the Fellowship encounters various strangers that either help or hinder their quest. The helpful strangers, like Tom Bombadil, are perhaps the most significant because they represent the inherent goodness that endures even in the face of great evil. This is thematically important because The Fellowship of the Ring is, in part, about what happens when people resist the corrupting influence of power.