It mentions "rolling over Beethoven," a clear reference to both the Chuck Berry classic and ELO's own 1973 hit cover of "Roll Over Beethoven".
It was originally titled "Motor Factory" and featured entirely different lyrics before Jeff Lynne reworked it into the rockabilly anthem known today. ELO - Rock'n roll is king
"Rock 'n' Roll Is King" was one of ELO's last major hits during their original run: It mentions "rolling over Beethoven," a clear reference
Lyrically, the song is a "love letter" to rock and roll. It contains several self-referential and genre-specific nods: It mentions "rolling over Beethoven