The wizard Gandalf would be an obvious character for Harry to interact with. They are both wizards, though from different worlds. They could share their knowledge of magic, and Gandalf could guide Harry in the ways of Middle Earth while Harry could introduce some new magical concepts to Gandalf.
Harry might also interact with Aragorn. Aragorn is a great leader, and Harry could offer his help in the battles against the forces of evil. They could become friends, and Aragorn could teach Harry about the ways of the men in Middle Earth while Harry could show Aragorn some of the wonders of magic from his world.
Maybe Harry could use his magic skills to face the various challenges in Middle Earth, like fighting orcs or helping the hobbits on their journey.
Well, he might be really confused at first. Middle Earth has its own unique magic system and races. Harry, with his Hogwarts - trained magic, would have to adapt. He could probably make friends with some of the elves, like Legolas, as they both have a sense of honor and skill in archery. And his encounter with Gandalf would be really interesting, as they are both powerful wizards in their own ways.
Obviously, Buffy would be a major character he'd interact with. They could start off as wary of each other but then grow to respect one another's fighting skills. Giles too, as he has a wealth of knowledge about the supernatural, and he and Harry could have some interesting discussions about different types of magic.
The wizards in Middle - earth might be both amazed and a bit wary of Harry's magic. For example, Gandalf would probably be interested in Harry's ability to Apparate. And Harry would be in awe of the different races. The hobbits might be a bit scared of him at first but then warm up to him when they see his kind nature.
The characters from Hogwarts would likely be very curious about the races in Middle - earth. For example, Hermione might be eager to study the elves and their knowledge of magic. And the Middle - earth characters would be both cautious and intrigued by the sudden appearance of these strange wizards. Aragorn might see them as potential allies or threats depending on their actions.
He might interact with Luna Lovegood. She's always open to new and interesting conversations, and she could approach Harry when she sees him alone.
There are many potential characters. The teachers at Forks High School for sure. Harry could have interesting conversations with them. Also, if there are any other supernatural beings in the Forks universe in this fanfiction, like werewolves, he could interact with them. And of course, the students who are into different clubs and activities at the school. He might bond with the science - loving students or those on the school newspaper team, sharing his own experiences from Hogwarts in a veiled way.
When it comes to interacting with humans in Middle - earth, like the soldiers of Gondor, he could offer his help in fighting against the forces of evil. He might use his knowledge of combat magic from Hogwarts to aid them in battles. And with hobbits, he would likely become friends easily, sharing stories of his adventures in the wizarding world.
In this fanfiction, Harry Potter would interact with the Queen in a very unique way. Since he is used to the hierarchical system in Hogwarts, he would understand the importance of showing deference to the Queen. He could offer her a magical gift, like a charm that gives good luck. And the Queen, being curious, might ask him about his world. Harry would have to be careful not to reveal too much about the wizarding world to the muggles, but still satisfy her curiosity. There could be some misunderstandings too, for example, when Harry tries to explain some magic concepts using wizarding terms that the Queen doesn't understand.
Harry's magic is more about instant spells using his wand. In Middle Earth, magic seems more subtle and connected to the land. But Harry's powerful offensive spells like the Stunning Spell could be quite effective. His ability to fly on a broomstick would be a unique advantage. However, the wizards in Middle Earth, like Saruman and Gandalf, seem to have a more profound understanding of the deeper magic of the world.