When answering your forum thread I didn't realise you wrote metal. Since it's my area too I thought I'd give you some constructive feedback.
Firstly - awesome song. It's a little repetitive at times, a couple of bits drag on for too long but the ideas are great and it all comes together really nicely. I found myself getting lost in it at times. It's a heartfelt piece of music, I can feel it.
Since you were looking to improve your mixing (remember, this is different to mastering, which I will discuss later), this is where I can help you. I'll break it down section by section.
Lead Guitars - Every song emphasizes different aspects in different ways. I felt that the lead guitar was the most important part of this track so let's talk about that first. Your lead guitars are quite crowded in this. The sound is nice but I feel you scooped out their body and they sound flat/squished under the power of the rhythm guitars. The key here is to scan through all the frequencies created by your guitar and distortion to find its fundemental frequency, the one that gives it body. Once you find it (my lead guitar sits around 500-800hz), carve out this space from other instruments (in this case rhythm guitars mainly) and boost the lead there. This will allow the lead guitar to breathe. Also consider using some reverb/delay to let the lead guitar "float" over the other instruments. Reverb creates space around an instrument like a cushion of air. Just don't use too much!
Rhythm Guitars - The meat and bones of any metal song, rhythm guitar needs depth and power. High-pass any frequencies below 100hz to get rid of any mud (and to leave space for the bass guitar) then boost the low mids (200-300hz) to give it "balls". Scoop out a touch in the mids to leave space for the lead guitar, cut out a chunk from 1.5k-3k if you add vocals, then depending on if it needs it, you might want to add a small peak in the 4k region for clarity. Not always though, this will bring out other issues so use it carefully (like hiss etc).
Bass - Is there a bass guitar in this? If so I can't hear it. If there isn't, it needs one!
Drums - The drum kit is the basic "metal" kit or something right? I hear it everywhere. It's way too dry, try to make it your own by EQing each element and adding some processing to the snare. The snare has its depth/body around 300-500hz (notice how this fits in with the two previous instruments?). If you add a short but WIDE reverb the snare will come alive and sound powerful. Again, don't overdo it. Feel free to experiment with drums, just know that it took me years to get mine right so don't worry too much at first.
Polish - Your track has a definite "mono" feel to it. Did you pan the guitars etc? I tend to pan my rhythm guitars around 80-85%. The lead guitar should be more central. If there's only one melody playing, have it dead centre. If there are two, pan them 20-40% at most. The snare, kick and bass guitar should always sit in the middle. They are the foundation and hold the song upon their walls. Never pan those unless it's for effect.
Mastering - Do you have any mastering plugins? If not, you could try Melda Production's free mixing plugins. They come with some excellent effects such as a stereo widener. You could use this JUST A LITTLE (never more than a few %!!!!! Up to 10 I'd say, until you get a high quality mastering plugin such as Ozone 6. No matter how good your ear thinks "more" is "better", it isn't, for more complicated reasons such as creating phase issues...) to make some aspects of your song wider such as rhythm guitars.
Here you could also add some tube or tape distortion, gently just to add character.
My final tip for you - if you want your guitars to sound HUGE, turn the distortion effect way down. Counter-intuitive right? But distortion is a form of compression and a compressed sound is lifeless and small. Less overdrive means more depth to the sound and besides, once you have two guitars playing Left/Right, they'll sound bigger anyway.
Hope this helps! Let me know if you update the song with this advice or follow it for a future one, I'd be happy to feedback again.