Brad Paisley will appear on this season of American Idol as a guest mentor, offering guidance to the competition’s top 20 hopefuls. He and Underwood had a successful run together as co-hosts of the CMA Awards for 11 consecutive years. Keke Palmer will also serve as a guest mentor this season on the show, which airs Mondays from 8-10 p.m. A three-time Grammy winner and member of the Grand Ole Opry since 2001, Paisley has written 21 of his 25 No. 1 hits, and his past works have amassed nearly five billion career streams.