There is a reason why the music of Queen is so heavily featured in the soundtrack of Good Omens - beyond, of course, the simple reason that adding Queen songs into anything makes it inherently better.
To many, Good Omens is the literary equivalent of a lost recording of The Beatles and The Rolling Stones having a jam session. The 1990 comedic novel about the end of the world, which has been described as what it would be like if Monty Python remade The Omen, was co-written by British authors Neil Gaiman and Terry Pratchett relatively early in their respective careers. Both writers went on to become best-selling, critically-acclaimed authors, whose works were adapted for stage, screen, radio, television and video games. Gaiman personally wrote and oversaw the adaptation of the new Good Omens series, as it was Pratchett's last request of Gaiman before his death in 2015.
The novel Good Omens contained a running gag based around Gaiman's reported belief that any music recording left in a car for more than two weeks would magically transform into a Best of Queen album. As the book progressed, any time the demon Crowley attempted to change the music in his car while he was driving around, he would find it impossible to escape the voice of Freddie Mercury. Sadly, the joke doesn't work in these days where physical media is dying out and even Crowley's vintage 1934 Bentley is outfitted with a satellite radio receiver. This is why many moments in Good Omens are set to the music of Queen, matching those scenes in the original novel which noted certain songs playing in the background.
"Bohemian Rhapsody" is used the most, particularly in the first episode, with the demon Crowley (David Tennant) arriving at his meeting to discuss the coming of the Anti-Christ as Freddie Mercury sings that "Beelzebub has a devil put aside for me." Snatches of the song can also be heard as Crowley receives his orders on where to deliver the infant Anti-Christ and just before his arrival at the hospital, which is set to "It's A Hard Life." "Bohemian Rhapsody" shows up again at the end of episode 5 and at the start of episode 6 (though different clips are used) when Crowley dramatically arrives at the USAF base where the end of the world starts, at the wheel of his burning Bentley.
Episode 2 plays "Days Of Our Lives" just before Crowley collides with bicycle-riding witch Anathema Device and "Bicycle Race" blares in the background of Crowley's car as he gives her a lift. Episode 5 opens with Crowley racing through the streets of London to "You're My Best Friend," as he tries to reach the book shop run by his best friend, the angel Aziraphale. When Crowley discovers the shop is on fire and concludes that someone has killed Aziraphale, he emerges from the flames to Queen's gospel-inspired hit "Somebody To Love," having finally come to grips with his feelings for the angel.
"Another One Bites The Dust" is used in episode 5 of Good Omens, as Crowley becomes stuck in traffic on the M25 freeway around London and "I'm In Love With My Car" blasts forth as Crowley drives through the wall of fire surrounding London. Queen's power ballad, "We Will Rock You," plays as Crowley and his flame-engulfed Bentley "rock the world" of an unfortunate neighborhood watchmen in the village of Tadfield, whom Crowley asks for directions while seemingly unaware that his car is on fire. Finally, a brass band can be heard playing "Lazing on a Sunday Afternoon" as Crowley and Aziraphale meet in the park just before their respective abductions.