Complex sentence: The Canadian skate punk band Sum 41 broke into the mainstream in the early 2000s; its song "Fat Lip" peaked at number 66 on the "Billboard" Hot 100 chart and number 1 on the Modern Rock Tracks chart.
Split into simpler sentences: The Canadian skate punk band Sum 41 broke into the mainstream in the early 2000s. Their song "Fat Lip" peaked at number 66 on the "Billboard" Hot 100 chart and number 1 on the Modern Rock Tracks chart.