some good songs "are"
embody the invisible by in flames, in flames has a lot of harmony, especially in that song
Quote by beadhangingOne
There is no music but metal and muhammad is its prophet.
Iron Maiden - Anything. Anything.
Boston - "Piece of Mind", "Don't Look Back", "More Than a Feeling"
Metallica - "Master of Puppets"
Led Zeppelin - "Bring it on Home", one part in "Ramble On"
Pixies - "Monkey Gone to Heaven"
Black Sabbath - "A National Acrobat"
That's all I can think of off the top of my head. Those should keep you occupied for a while.
ohhhhh IN FLAMES - serious harmonizing there, especially in the older material.

try these: in flames - the jester race
carcass - heartwork
in flames - acoustic medly (instrumental)
in flames - dialogue with the stars (instrumental)
arch enemy - stigmata

and yeah lots of iron maiden stuff too...

harmonized riffs are so great
Megadeth- Hangar 18
Major of 7 String Legion 7 > 6

Carvin DC747
Ibanez RG2228
Schecter Avenger Custom Shop
and my baby....
Gibson Explorer Studio
Noone mentioned A7X yet!
Pretty much all of there songs have harmonized guitars.

thin lizzy are the kings at this, even if you particularily like there music, theres still alot to be learnt by playing the stuff
Any Iron Maiden.

Also, if you're willing to branch out from just metal, then Thin Lizzy's 'The Boys Are Back In Town' is a kickass song with brilliant harmonizing.