Google Polymer looks like a simple way to make material designed web pages. I am developing a native Android application and would like to make it material designed. My question is, can I use Polymer for native Android applications?
No, you cannot use Polymer to build a truly "native" Android app. Although there are frameworks such as Phonegap which would allow you to build an app using web technologies and then compile into an Android app.
If your goal is to make an app that follows material design patterns, I suggest you get started by reading the official documentation on the subject: Creating Apps with Material Design