What are some alternatives?
When comparing metro-bootstrap and GroundworkCSS, you can also consider the following products
Bootstrap - Simple and flexible HTML, CSS, and JS for popular UI components and interactions
Metro UI CSS - Metro UI CSS a set of styles to create a site with an interface similar to Windows 8.
Semantic UI - A UI Component library implemented using a set of specifications designed around natural language
Foundation - The most advanced responsive front-end framework in the world
Material Design Lite - Material Design Lite Components in HTML/CSS/JS