It could be really interesting. Imagine Daryl from The Walking Dead in the world of Twilight. Daryl's survival skills would be put to a very different test. In the Twilight world, there are vampires and werewolves. Daryl, being used to fighting zombies, would have to adapt to these new threats. Maybe he'd form an unlikely alliance with the Cullens against a new kind of undead that combines the traits of zombies and vampires. His crossbow would be a unique weapon in that world full of supernatural powers.
A possible scenario in this crossover fanfiction could be that Daryl stumbles into the Twilight universe through some sort of portal. He initially thinks it's a different part of the post - apocalyptic world he knows. But then he starts seeing vampires and werewolves. The vampires, with their elegance and speed, would be a new kind of enemy for him. And Daryl's journey through this new world could also lead to him learning about different forms of loyalty and relationships, which are central themes in Twilight. He might even find himself in the middle of the love triangle between Bella, Edward, and Jacob, but in a very different way than the usual Twilight characters.