1. Blink-182: One doesn't have to dig too deep to realize that 5 Seconds of Summer were heavily influenced by the Mark, Tom and Travis show. Pop-punk bands claiming Blink-182 as a muse is nothing new, but given the tender age of the 5SOS guys, it's notable nonetheless. Luke Hemmings and company were younger than 10 years old when Blink could commonly be heard on the radio. They even covered "I Miss You" -- a track that dropped when Hemmings was only 7 -- back in their pre-stardom days (2011, to be exact).
2. All Time Low: These Maryland-based pop-punkers have never been shy about their Blink-182 influence, and in pop-punk's circle of life, the 5 Seconds of Summer guys are some of All Time Low's biggest devotees. The quartet responsible for jams like "Dear Maria, Count Me In" is one of only three influences named on 5 Seconds of Summer's official Facebook page, and on their self-titled debut album, they go one better. ATL frontman Alex Gaskarth co-wrote three tracks with the band: "Kiss Me Kiss Me," "End Up Here" and "Long Way Home."
3. Good Charlotte: The pop-punk community is still pretty split on Good Charlotte, but not 5 Seconds of Summer. "Good Charlotte is the reason I started playing guitar," Luke Hemmings said in a video on the band's influences. "That's where all of us started." And on their debut album, that's where 5SOS ended too. Benji and Joel Madden co-wrote the record's penultimate track "Amnesia" along with the band. Check out 5SOS' official influence video below:
4. Green Day: "Green Day's on the radio and everything is alright," goes new song "Long Way Home," as 5SOS shout out one of their most seminal influences. "We were brought up in the time of Green Day," says drummer Ashton Irwin. "That type of music has influenced us so much." Irwin was born the same year Dookie came out, so it's pretty clear he's talking about the band's American Idiot comeback era. We're not too sure we'd be down with a political 5SOS rock opera, but in terms of hooks and arena swagger, they fit the bill.
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5. Nirvana: If you've seen a few photos of the guys, you know that they've got a thing for Nirvana -- especially bassist Calum Hood, who seems to rock Kurt Cobain and Nirvana-themed apparel more than any of his bandmates (which is really saying something). And let's not forget the chorus of "End Up Here," which opens with the couplet: "How did we end up talking in the first place? / You said you liked my Cobain shirt." And guess what? According to most rock historians, Nirvana's music was almost as influential as their fashion influence!
6. Mayday Parade: Like All Time Low, Mayday Parade are another pop-punk band that gained popularity around the time the 5SOS boys were just starting high school. For one of their pre-stardom acoustic covers, the band covered Mayday's 2007 song "Jersey."
7. Busted: If Americans know of this British pop-rock band (who released two LPs and a series of hit singles in the early 2000s) it's probably through their songs "What I Go to School For" and "Year 3000," which were covered by the Jonas Brothers. 5 Seconds of Summer logged writing sessions with Busted frontman James Bourne and covered "Year 3000" for their acoustic YouTube series.
8. McFly: British pop-rockers McFly are so intertwined with Busted that they recently toured alongside them as the supergroup McBusted. And like Busted, 5SOS have collaborated in the studio with McFly bassist Dougie Poynter.
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9. A Day to Remember: You won't likely find circle pits and mesh shorts at a 5 Seconds of Summer show, but that doesn't mean the band doesn't have some (poppy) hardcore influences in its arsenal. The Florida-based pop-punk-meets-hardcore act has a few acoustic songs in its repertoire as well, so it's actually not too surprising that 5SOS went the ADTR route in its acoustic covers series.
10. Boys Like Girls: Rounding out 5 Seconds of Summer's trio of name-dropped Facebook influences (along with All Time Low and Mayday Parade) are Boys Like Girls, the pop-rock band best known for hits like "The Great Escape" and "Love Drunk." And lucky for 5SOS, they got to log some studio time with Boys Like Girls frontman Martin Johnson back in 2013. Although none of their collaborations made it to the debut album, Johnson has scored hits co-writing and producing artists like Avril Lavigne and Jason DeRulo.
Honorable mention: Loving band merch as much as they do, 5 Seconds of Summer have been photographed wearing the apparel of many more artists outside of this list. T-shirts they've been spotted in include -- but are not limited to -- the Rolling Stones, AC/DC, Sex Pistols, Joy Division, New Order, Bad Brains, Def Leppard, the Ramones, Jimi Hendrix, the Strokes, Iron Maiden, the Misfits, Jawbreaker, Queen, the Clash and, as evidenced below, Less Than Jake: