"Lux Æterna" is about the powerful connection between Metallica and their fans, celebrating the community they've built together. The lyrics, like "a sea of hearts beat as one unified" and "never alone for the feelings alike," highlight this shared experience. The title itself means "eternal light" in Latin, suggesting an enduring bond. This thrash metal song, described by James Hetfield as similar to the new wave of British heavy metal, was a "fun" and simple track to write for their 2023 album, 72 Seasons. Playing it feels like tapping into that collective energy and shared passion.