Michelle teamed up with Saturday Night Live comedian Jay Pharaoh and College Humor back in December last year (15) to promote a rap video urging kids to go to college.
In the video, she raps, "South Side Chicago, we all know / We had to do overtime every night to make it tomorrow."
The lyrics struck a chord with rapper Common, who is from the city's South Side.
When asked by a TMZ reporter if he'd seen the First Lady rapping, he laughed, "I really loved that, man. I love her. She said something about the South Side... it was good, man. You can tell she was passionate.
"I seen that with Jay Pharaoh, and she was good, man. She was good. She's the best. I was like, I wanna sample something what she said about coming from the South Side. She's good. I would rhyme with her on something because she's that dope."
Common, who won an Oscar last year (15) with John Legend for their song Glory from the movie Selma, also said he would be more than happy to work on music with the First Lady and her husband, President Barack Obama.
"For the President and the First Lady, I'd do anything. I'd do some music with them for sure," he joked.