Hey,
Im living in Germany right now and I could tell you the greatest place in the NRW where you could find the metal entertainmetn you are looking for.
If you are infact locationed in Düss...There is Essen, Köln, Bochum and Dortmund...
Essen has a very big club called the Roxy...on saturday nights many of the Wacken Forum members gather there...Also there is a club called the Zeche Carl...almost once or twice a month there are the greatest metal bands in europe playing there..So far I have seen Opeth, Samael, Necrophobic, Macabre, Satyricon, etc.
Dortmund has a club called Spirit...its okay I guess..the crowd in my opinion is a little too young for me...but the metal they play is pretty good..
Köln also has many attracts the Cave Valhalla and la lic or what ever. They also have many concert halls and clubs..but they dont have as many bands that you would probably like playin in them..as compared to Essen, Dortmund, Bochum etc.
So all these cities are relatively close to one another..so have fun.