“There is a metric ton of books in my backpack” is an example of hyperbole, which is an exaggerated statement not meant to be taken literally, emphasizing the heaviness or volume of the books.
“My backpack stubbornly refuses all attempts to lift it, even when I use both hands” is an example of personification, which is a literary device where human traits or behaviors are attributed to non-human objects or abstract concepts, in this case, describing the backpack as if it has intentions or a will of its own.