Most Flex developers have seen and used the [Bindable] tag but not many know what this tag does or even what it is. [Bindable] is what is known as a metadata tag. Metadata tags are special tags that are inserted in your source code that give the compiler information on how to compile the application. These tags aren't actually compiled into the generated SWF file but provide instructions on how the compiler should create the SWF. There are 12 documented metadata tags. This article will offer definitions of these metadata tags and give examples of their use. By the end of this article you will understand when and where to use metadata tags in your Flex 2 applications.