OK.
If
1) "melodic" means "based on memorable tunes", or "based on a sequence of pitched sounds",
and
2) you like "Human" and "Symbolic" and you are enlightened enough to appreciate that they totally rule because they are so dark and memorable
I suggest that you ignore about half of the suggestions in this thread for starters. Then - if indeed "memorable, tuneful and dark" is what you are looking for - you should try:
Carcass - ('Necroticism', 'Heartwork')
Entombed - ('Clandestine', 'Wolverine Blues')
Pestilence - ('Testimony of the Ancients' - I can't believe noone's mentioned this yet)
At the Gates - ('Slaughter of the Soul', 'Terminal Spirit Disease')
Dismember - ('Indecent and Obscene' - earlier stuff is primitive, later stuff sucks)
Morgoth - ('Cursed' - the best death wannabes ever)
Demilich - (download entire album at their official site
http://demilich.doesntexist.com/)
Morbid Angel - ('Domination', 'Covenant')
You might also want to check out Cynic, as they are basically the Human-era Death lineup without Chuck - hence no songs and no fucking power whatsoever. Musos trying to be clever, thus succeding in making the wankiest non-JazzFusion record the world had ever seen... until Martyr's second studio album. The first Martyr album is pretty good and still memorable. By the second release they had completely disappeared up their collective arse.
IF by "melodic" you meant "wannabe power metal", "based on major scales", "mind-meltingly predictable and nauseating", "based on the worst folk melodies ever", or even "worthy of nursery rhyme-dom", then I recommend:
Turisas
In Flames
Thales (from Finland)
Nightwish (also from Finland)
Eternal Tears of Sorrow (in Finland, they really like their metal 'melodic')
Desultory (one of the pioneers of the whole 'melodic' thing - from Sweden this time)
Callenish Circle (what ATG would have sounded like had they been shit)
Stratovarius (another Finnish contribution - ok they're power metal, but they're so 'melodic' I had to put them in somewhere; and actually I think Turisas are also Finnish as well as being rubbish)
Dragonforce - (while we're on the ever so slightly homoerotic subject of powermetal, check out
http://dragonforce.com/ see the 'fan art' section on the site for an insight into the mind of the 'power metal' fan)