Explanation:
1. It's a metaphor.
2. Two things that are being compared is your emotions, and feelings.
3. A person can probably feel like a plastic bag because they probably feel useless, and since plastic bags are considered "one time uses" by some people, they end up feeling like they're not needed again.
4. (This may not be correct) The phrase is a similie because someone could feel let down that they probably don't care anymore, or maybe they're let down too easily.
5. (This is probably not correct again, sorry) Two things that are being compared is how you feel so thin, meaning that if you're not big enough, like a firework, you're useless, and emotions becoming negative.
6. No, because it would feel like people are building you up just so they can put you down.
7. This is a metaphor because no one can be a firework.
8. Katy Perry means that when you're a firework, you're bold and unique, since fireworks are different than others.
