What are some alternatives?
When comparing metro-bootstrap and w2ui, 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.
Vue.js - Reactive Components for Modern Web Interfaces
Material Design Lite - Material Design Lite Components in HTML/CSS/JS
UIKit - A lightweight and modular front-end framework for developing fast and powerful web interfaces