Thirty Seconds to Mars Talk 'Explosive' Single 'Walk on Water' at iHeartRadio Festival: Watch

Already hitting No. 7 on Billboard's Alternative Songs Chart, <a href="/artist/431915/30-seconds-to-mars/chart">Thirty Seconds to Mars</a>' latest single, "Walk on Water," is one of the fastest-climbing songs of the year.

Backstage at this year's iHeartRadio Festival, the band discussed the song and how the success of the song surprised them.

"We haven't put out music in four-and-a-half years," lead singer Jared Leto explains. "We expected a marathon."

Leto said things have "never been easy" for the band and called "Walk on Water" an "explosive" song that they're really excited about.

"It's a song that speaks to the times that we're living in," Leto said. "It's a song about standing up for what you believe in."

Watch the full interview in the video above.