Chester Bennington's bandmates are remembering him for his musical talent ... and also the demons that ultimately led to his suicide.

Linkin Park posted an open letter to Chester in which they thank the fans for the outpouring of love and support, and say of the singer ... "You touched so many lives, maybe even more than you realized." It sounds like they didn't see any warning signs before Chester took his own life because they say, "Talking with you about the years ahead together, your excitement was infectious."

The band addressed their frontman's demons too -- "You fearlessly put them on display, and in doing so, brought us together and taught us to be more human."