Martin, 37, recently attended band's iHeartRadio album release party for 'Ghost Stories' in Burbank, reported People magazine.
"We made the decision about 15 years ago that being open and vulnerable would be the thing that we would do. That means that what we sometimes lose in poeticism, we gain just by truth... I won't be hiding any of my songs," he said.
"That's something that means something to me, but I never want to say what it's about because it might mean something to someone else. Hopefully, whatever we're singing is real," Martin added.