– Sales: 4,813,000

True to its name, Linkin Park’s “Hybrid Theory” blends electronic music, hip-hop, and heavy metal. While the group wasn’t the first to bridge multiple genres, Linkin Park did carve out its own unique aesthetic and sensibility in the process, becoming nu-metal pioneers. While recording the album, the band had to fight tooth and nail against the record label, which suggested bringing in a guest vocalist on certain tracks. Sticking to their guns, bandmates refused and instead made the debut album they wanted to make, which became the biggest-selling debut of the 21st century. Things came crashing to a halt after the untimely death of lead singer Chester Bennington in 2017.