Eternal Sunshine is a
pop and
R&B album that features elements of
dance music, especially
synth-pop and
house music. Helen Brown of
The Independent described it as a "slow-fizz pop" album, consisting of mid-tempo
synths,
strings and muted guitar. Jem Aswad of
Variety felt that Martin and Salmanzadeh imbued the album with a "very
Swedish vibe and structure to the tracks" inspired by classic pop, a style atypical of
Anglo-American musicians. Lyrically, the album is a combination of both "ultra-confident and entirely self-deprecating" themes, inspired by Grande's personal relationships.
Billboard described it as an introspective record—one in which Grande reflects on herself as she enters her thirties. The second song, "
Bye", was described by Grande as the hardest song on the album for her to write, saying "It was hard for the reason that I desperately didn't want it to sound like a 'fuck you.' I wanted it to sound like, 'I need to leave, so bye'". Grande wanted the song to have a sense of self-awareness and accountability, rather than being completely dismissive. It is an uptempo
dance-pop number with influences of
disco and
Philadelphia soul. The third track, "Don't Wanna Break Up Again", is a gloomy, '90s influenced pop and R&B song that discusses conflicting feelings Grande has towards the end of her relationship with her partner. The album's interlude, "
Saturn Returns", prominently samples a YouTube video of astrologer Diana Garland, as she discusses the importance of the age of 29 in a person's life. She urges the listener to "wake up" and "sort out who you really are" before the album's fifth and title track. The interlude fades directly into "
Eternal Sunshine", during which Grande seems to come to terms with the faults of her partner and their relationship. In the track, she hints that her ex-husband, Dalton Gomez, may have cheated during their marriage and displays an uncertainty towards their relationship over an "R&B-pop" beat. "
Supernatural", the sixth track on the album, has a low-tempo beat. The lyrics are about how Grande is in love with someone and is inseparable. Grande lets this love take over her entire state of mind. The lyrics also show that Grande is healing from heartbreak and is ready to love again. Billboard ranked "Supernatural" number eight out of
Eternal Sunshine's tracks and compared it to "
Breathin'" from
Sweetener, as both songs are "undeniable home runs and surefire pure-pop smashes."