When using this theme you will NOT see CERTAIN menu items unless a image is loaded 
or a layer is created.You will only see the image and that is normal.Create one 
layer and you will see all the menu items as normal.

Tested in Parthas new foreground tool 2.7.3 fork (RGGJAN) -  http://partha.com/
Parthas Gimp-2.8.1 install 
Partha and SamJ's Portable Gimp-2.8.1 ONLY!

Where everything needs to go

Metal Dark folder
F:\Gimp-2.8.1_Portable\Gimp-2.8.1-32bit-Partha\share\gimp\2.0\themes

gtkrc file needs to go in BOTH these locations.
\etc\gimp\2.0
\pref_1    OR    \.gimp-2.8 folder

DLL files
\lib\gtk-2.0\2.10.0\engines 
IF the gtk-2.0 and the subdirectories are not present create them.

For further help - contact - Rod at GimpChat.com