The two acts will join forces on Monday night's (04May15) show and Imagine Dragons frontman Dan Reynolds can't wait.

He says, "IMAGINE REO SPEEDRAGONS was destined to happen since the day Zeus thrust his mighty bolt to the earth."

Previously on Kimmel's Mash Up Mondays, Haim teamed with Morris Day, Kenny G teamed with Warren G, and Weezer teamed with ZZ Top to form Wee-Z Top.