Metal rhythm

Okay, as some of you know, I have been doing some serious work on my rather abysmal metal rhythm chops for some time now, and I think I've finally made an improvement. As well as standard palm-muted power-chord riffing, I can now do fast triplet gallop-picking a la "Battery", drop-D dissonant chords, pinch-harmonic-infused riffs like "Cemetery Gates", percussive muting like "Train of Consequences", and, of course, some fast-as-you-can sixteenth-note picking, "Angel of Death"-style. My question is, are there any important metal rhythm techniques that I'm missing here, and if so, what are they?
Cheers, guys. :)

Knowing the techniques you have learned is important BUT! playing them together to create metal riffs is probably your next step.

Take time to sit down and try to mix all the techniques you've learned. Improvise going from gallop to fast 16th notes, punch-in a wicked pinched harmonic into a dissonant chord..... you get the picture.

alternate between palm muted and unmuted riffs until they are fluid.

ALso, practice mixing tempos and switching between riff in 8th and 16th notes so that you are able to stop and go at will to different sections/riffs.

Learning techniques is a necessity to get you to create your own sounds/riff so don`t forget to jam a lot ;)

A realy cool old-school metal track that helps with alt picking over two strings is "Alice in Hell" by Annihilator. http://www.youtube.com/watch?v=bKGTCzcgji0
Dated now with pretty naff singing but it's a good riff with a neo-classical feel, good for practising the alt picking.

Thanks everybody! :)