Material design introduced by Google, became a new design standard for the latest version of Android, Chrome OS and web apps. It unifies visual, motion, and interaction design across different types of devices. Material design modeled after tactile materials like paper and ink with fluid animation and lighting.
Polymer brings these paper elements to life on the web. It is a library for creating Web Components, which are a set of W3C standards and upcoming browser APIs for defining your own custom HTML elements.
With Polymer you can achieve achieve beautiful material design app layouts, awesome transitions and scrolling effects. Here are some nice examples:
Read the complete guide on material components and how to deal with Polymer library.