The lead singer from the pop-rock group has been drafted in to write tracks for the Material Girl’s new album, which will be released in 2015.
'It’s her best stuff in over a decade - it’s really strong,' he told the Daily Mirror.
But the 35-year-old musician added: 'The tracks I’ve done with her are really hard to explain.'
Ryan, who performed at Capital’s Jingle Bell Ball on December 6, has composed songs for the likes of One Direction, Leona Lewis and Ella Henderson.
Madonna has also teamed up with Avicii, and their track Rebel Heart was leaked online with another song, Wash Over Me. The singer admitted the breach of privacy 'broke her heart'.
And Ryan revealed his concerns that the leaked tracks could have been his collaborations with her.
'I was actually working on something with Madonna when her tracks leaked,' he said. 'So I panicked because I thought it was the song I was working on, but luckily it wasn’t. People have way too much time on their hands.'