I was just looking around about classical music,and i saw that tremendous post of this metal-fan!Although it is written 2 years ago,i am not able to not answer to him!As a former heavy metal fan in the past,with exactly the same ''taste'' as yours to music,i must admit that 5 years ago i had exactly the same problem-question.I wanted to find sth epic,intense,''brutal'',angry,loud and heavy instrumental,orchestral piece in classical music,cause it was the only way to find a connection between metal and classical.So after a huge long journey i decided to write some propositions to you.Well,first of all,i have seen the posts that all the other members mentioned,and i agree almost 80%.But,i must say to you,that as a metal fan,it won't be easy for you to ''understand'' in some way,WHY the mentioned pieces(Mahler symphony 6 for example) are epic and angry.That is because your ear is not used in that kind of music.So,don't be surprised if you don't feel anything ''epic mood'' when you hear these pieces.They are epic,and angry,but it wont be easy in the first years to ''catch them'' by ear.Now,personally,i believe that the epic instrumental you are searching for is this:Verklarte Nacht-Arnold Schoenberg(Karajan/Boulez).It is the maximization of power,will,intensity,darkness,the whole piece is a monstrous,alpine power that destroyw everything,so scary and epic!But i think in the first listen you will find it a bit difficult.Another angry piece is that:Anton Bruckner-Symphonies 8,9.Bruckner was the MASTER OF EPIC SYMPHONIES,these are not just powerful...THEY ARE THE POWER ITSELF!!Epic!Check out Celibidache or Karajan's versions.Also,a true epic,angry monster is this one:Jean Sibelius-Finlandia,Oceanides,Symphony 2,and Tapiola.Especially the Karajan or Vanska version of Finlandia is a true masterpiece!I must add of course,Richard Strauss,and the symphonic poems Also sprach Zarathustra,Alpine Symphony,Metamorphosen and Tod Und Verklarung.My favourite is the Alpine Symphony.A real,cold,harsh,spiritual power!But Strauss,i must admit,is too ''difficult'',i mean if you hear Metamorphosen,you will see that it's perfect,but in a more spiritual level,you have to ''approach'' it with your mind more and less with your emotion,maybe you know what i am trying to say.Here, i mention also the Lyric Symphony from Alexander Zemlinsky,the Planets from Gustav Holst,Rued Langgaard has composed some true,epic,angry,superhuman BEASTS,most of Mahler's epic symphonies,such as the 1,2,3,5,6,8(they are difficult too!)and of course Dmitri Shostakovich symphonies 5,8,11,10,12 but especially 5 and 10.In my opinion,the ''easiest'' of all them to begin with is Shostakovich.Check him first and then reply to me with your impressions!!I am looking forward to hear,metal fan!