Perhaps most well known for his portrayal of the villainous Apophis on the Showtime science fiction series Stargate SG-1, he is also notable for his starring role in the 2007 Canadian movie A Winter Tale, as well as for his role as Morris Winston on the drama series Da Vinci's Inquest.
Early in his career, he played a small role in the 1982 movie Heatwave.
In 2009, he launched a blog titled the Ackeelover Chronicles.
A native of Kingston, Jamaica, he later lived and worked in Canada. His brother Stephen Williams had a career as a television director and producer for the hit series Lost.
He appeared with Winston Rekert in nearly seventy episodes of the Canadian television series Neon Rider.