When someone says “You’re like a vampire!” to a living person, that’s a simile, a comparison using like or as. When some says “You’re a vampire!” to a living person, that’s a metaphor, a comparison NOT using like or as. Living people are not actual vampires because vampires are DEAD THINGS that, by definition, are not alive – otherwise, they would not be a vampire. Feel free to compare all you like, but the following is the ONLY definition of a vampire:
a mystically animated corpse that imitates its living victims so it can feed off of their blood.