Google has the following to switch between Desktop Mode and Metro UI in Google Chrome:
Switch between Chrome on the desktop and Chrome in Windows 8 mode
That page also shows how to switch between regular window and incognito window, add a secondary tile to the Start Screen, and info about not all plug-ins are supported due to the Pepper API.
In addition, Softpedia has a registry key if you just want to force Chrome to use Desktop mode:
Google Chrome Stuck in Windows 8 Mode – How to Fix It
HKEY_CURRENT_USER\Software\Google\Chrome\Metro
I think I like this 2nd 'fix' better since I prefer to use browsers in Desktop Mode anyway.
More in the article about the 'bug'.
Google Chrome really screwed up on this. They should have had it open in Desktop mode if you launch it from the Desktop, and in Metro UI mode if you launch it from the StartPage.