Mozilla has released an early version of its Windows 8 browser for testing by those working with pre-release versions of Windows 8 - and despite Microsoft trying to wean us off the name, it is called Firefox Metro.
The Firefox Metro Preview is in the latest nightly build of Firefox version 18 which isn't scheduled for general release until January 8, 2013. It is also referred to as "Nightly" by virtue of the fact that is currently being updated on a nightly basis.
The preview shows off some of new features that have been created for this version such as a "Metro" style Firefox start page with rectangular coloured panels on a grid representing bookmarks and recent history. The preview also includes support for "Metro" touch with swipe gestures and the touchable tab bar shown here.
It also supports Windows 8 "charms", Firefox Sync and has a simple version of the forthcoming Australis interface which has now been in development for over a year and is intended to make Firefox more usable.
However, as Mozilla Firefox developer Brian Bondy explains on his blog:
This preview will give you a glimpse of what Firefox on Metro will be like, but it is not meant to be complete. Several incomplete features will exist, which is normal, since we're still mid development for a beta version.