The group was performing Monday night in Miami when frontman Chris Martin announced the band was going to play a song in honor of the flood victims in Houston. But get this ... Martin said the band's never played it before and NEVER would again. Its only purpose -- to send love from Miami to Houston, currently underwater following catastrophic flooding.

It's an incredible rendition from a band that grew up admiring and listening to country music. Some of the lyrics, "I'm dreaming of when I get back to Houston" ... and "I'm dreaming of when Houston has no problems ... Oh Houston, you got to keep on keeping on."