https://blogs.msdn.com/b/b8/archive/2011/09/14/metro-style-browsing-and-plug-in-free-html5.aspx
No plug-ins allowed in IE on Windows 8. That means no Flash.Running Metro style IE plug-in free improves battery life as well as security, reliability, and privacy for consumers. Plug-ins were important early on in the web’s history. But the web has come a long way since then with HTML5. Providing compatibility with legacy plug-in technologies would detract from, rather than improve, the consumer experience of browsing in the Metro style UI.