I know it's a very old thread, but I just tried to install Metal Masters and it worked fine. When I asked tomse and xpect to try it they reported back that it doesn't work. Seems like this is one of the games that doesn't like to be zipped (as Retroplay recently discovered). With LHA the game works nicely.
Check the zone for the archive and thanks again to tomse and xpect for testing
Edit: The copy protection problem is still there it seems...