Great article outlining Windows 8 & Metro Accessibility:
“Our accessibility goals in Windows 8 are to: Improve the assistive technologies that are components of Windows, and provide a good experience with the Metro style UI. Provide developer tools that have baseline accessibility built in, so that accessible Metro style apps are available in the Store. Engage assistive technology vendors (ATVs) to adopt Windows 8 and build upon the accessibility scenarios. Each of these goals and audiences are discussed.”

? Original article:
http://blogs.msdn.com/b/b8/archive/2012/02/14/enabling-accessibility.aspx
From http://www.windows8tricks.net/2012/02/enabling-accessibility/