The first sentence, "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, used for emphasis.
The second sentence, "my backpack stubbornly refuses all attempts to lift it even when I use both hands," is an example of personification, as it attributes human-like qualities (stubbornness and refusal) to an inanimate object (the backpack).