Saxon singer Byford has released a statement about his pal's passing, revealing he and Lemmy were friends for 36 years.
He writes, "If you were his friend, you were his friend for life."
"He was a defiant rebel to the end who loved his music and never compromised," the rocker adds. "My heart goes out to his family and friends. The Motorhead organisation are in mourning for their friend and mentor to the management and their fantastic crew. Let's remember Lemmy as he wanted to be: as an iconic songwriter and lyricist and rock and roll rebel."
Byford concluded his farewell by adding, "Sad, sad day. Wherever you are, mate, give 'em hell."
Meanwhile, Black Sabbath star Iommi, who is also battling cancer, has joined bandmate Ozzy Osbourne in offering his thoughts about Lemmy's death.
A statement from the guitarist reads: "Very sad to hear of the passing of our dear friend Lemmy. He gave so much to the music business and was totally dedicated to his fans. His legend will never die. His life was all about the music, being on stage and a giving pleasure to others. Rest in peace, Lemmy. You'll be greatly missed."