The Black Eyed Peas star is working with Jackson on the "Thriller" singer's new album and says he is amazed with his unique voice.
Will.i.am said: "Man, he still sings like a bird. He could go anywhere. We have a real opportunity to do something here."
"It's either going to be really big or nobody's going to care. Ain't no middle ground on this one."
The music star, who is producing Jackson's first studio album for six years, recently revealed he was completely shocked to be asked to work with the former "King of Pop."
He said: "Michael called up and I thought someone was joking. I hear, 'Hello, it's Michael,' and I was like, 'Yeah right, stop playing!'"
"Then he said, 'I want to congratulate you on all your success. Do you mind if I call you in a couple of days at 4 pm?'"
"Then he started ringing me every day at 4 pm. So I started working on music for him on the tour bus."
