"Friday" uses the 50s progression, an I-vi-IV-V chord progression that hundreds of popular songs have used such as "Heart and Soul" and "Unchained Melody". According to Randy Lewis of Los Angeles Times, the familiar structure contributes to the song's catchiness, making it an "earworm". In a review for Rolling Stone, writer Matthew Perpetua described the vocals as having "a peculiar tonality that inadvertently highlights the absurdity of boilerplate pop lyrics," adding that the tone in the refrain "sounds unlike anything else in pop music." He noted the sound as being not entirely agreeable to listen to, but states that Black ultimately ends up "sounding like a distinct singer with an alluring sort of anti-charisma." The lyrics of the song speak about "hanging out with friends and having fun."
The concept for the music video is based on the lyrics and presented as a typical Friday for Black. She wakes up and goes to school, meeting her friends on the way. In the evening, after debating whether to sit in the front or back of a convertible, Black and her friends (Benni Cinkle and another girl) ride the car to a party. Wilson appears near the end of the song to deliver a short rap
