Question: what are bts fans chanting?
Answer: This is what's referred to as a “fan chant” by members of the K-pop community, and they normally take place during the beginning of, typically, upbeat songs. At the start of songs like “DNA,” “Idol,” “Boy With Luv,” and “Save Me,” fans chant the names of the members, in the order: “Kim Namjoon! Kim Seokjin! Min Yoongi!