I acknowledge that Michael started to sing when he was 5, but don't know what was the first song he sang on stage with Jackson 5?

At age 5, MJ did not create any new songs yet. The first song recorded kwa Michael was "My Girl" kwa the temptations. Michael was known for his covering of muziki when he was a child. He did not start to become world known until age 10 when he sang "The upendo wewe save, I want wewe back, abc, ill be there, etc."