For WPF (.NET) applications, I've personally used MahAppsMetro (http://mahapps.com/MahApps.Metro/ http://mahapps.com/MahApps.Metro/). For web, I've seen code52

For WPF (.NET) applications, I've personally used MahAppsMetro (http://mahapps.com/MahApps.Metro/ http://mahapps.com/MahApps.Metro/). For web, I've seen code52's metroCSS (https://github.com/Code52/metro.css/ https://github.com/Code52/metro.css/) and olton's Metro UI CSS (http://metroui.org.ua/ http://metroui.org.ua/) Both are full-blown frameworks with grids and everything and I've tried them out for my needs, but most libraries are too over the top. I needed something more stripped down for buttons that can work with Bootstrap or with my own handmade disaster. On a sidenote, the day Microsoft adviced and pushed developers to stop calling it "Metro" and call it "Modern UI" instead (http://gizmodo.com/5933580/on-second-thought-microsoft-is-calling-metro-modern-ui-style-now http://gizmodo.com/5933580/on-second-thought-microsoft-is-ca...), really got their own ecosystem off balance.