She sings: “Baby, you're a firework. Come on, show them what you're worth” while everyone shows their true colors like fireworks. The firework itself symbolizes courage, and lighting it symbolizes the strengthening of that courage. This illustrates that everyone comes together and reveals themselves like fireworks with the idea that they are "even brighter than the moon", a lyric from the song. No matter what flaws people possess, they are still seen as unique, brilliant, and capable of doing whatever they want.