In particular, the diffvec vectors all express relationships from the metalwork domain (e.g., 'heavymetals' or 'annihilator-metal'), which reflects the fact that the music-related interpretation of the word 'metal' is not its dominant sense.
since our relation vectors are exclusively learned from sentences where both words co-occur ('heavy' and 'metal' in this example), the vector for 'heavy metal' clearly captures the musical sense (see e.g., 'thrash-metal' or 'glam-metal' in the original space).