According to former vocalist Adam Gontier, "Pain" is "a song about feeling like you're constantly numb to things around you, thanks to your own actions, and it's about being sick of that feeling."

"Pain" has become the band's biggest hit to date. It reached number one on the Billboard Modern Rock Tracks chart for four consecutive weeks, becoming their biggest hit on that chart to date but it stayed on the chart for 30 weeks where the prior single Animal I Have Become and next single, Never Too Late stayed longer on the chart at 41 weeks and 43 weeks respectively. On the Billboard Hot Mainstream Rock Tracks chart, it reached number one and stayed there for thirteen consecutive weeks. It also hit number 44 on the Billboard Hot 100, becoming their first single to chart in the top 50 of the Hot 100 and their highest charting single to date.

"Pain" also held the number one spot on many Canadian rock stations for weeks, and was the most-requested song ten weeks in a row. It also reached number one on the MuchMusic Countdown.

The song was featured on episodes of Criminal Minds, CSI: NY, and Ghost Whisperer, and is a playable song on the music video game Rock Revolution & Rock Band 3.

"Pain" was re-released to pop radio on June 3, 2008.

The music video, directed by Tony Petrossian, features the band playing the song in what looks to be an abandoned mansion, and it also features shots of troubled youths who are lip-syncing to the song. At the end of the song, everyone (youths and the band members alike) is shown to be tattooed with a red "X" on the back of their necks.

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Wikipedia