I think we need to have a quick lesson in music genres... I cant believe you just called screamo metal.... Prepare for an epic post of longness...
Normally I dont do much hardcore... A band has to be exceptional in this genre to grab my attention, such as:
http://www.youtube.com/watch?v=6_849RctCvI/
Hardcore is like hard rock with screamo vocals... Usually you can understand these guys better than you can:
http://www.youtube.com/watch?v=A9CnuqNKOYE&feature=related
Screamo... Which is technically the "hip" term for post hardcore is... well rather dumb if you ask me. I've found little bands (2 In all reality I think...) in this genre that can hold my attention for more than a few seconds... It's post hardcore because it takes alternative hard rock stylings with metalcore style breakdowns, (metalcore is a part of the Hardcore family tree) and puts them over even usually inane lyrics and even worse sounding screams and screeching. One of the few bands I can enjoy in the post hardcore family is(notice the different style guitar playing over post hardcore, and hardcore):
http://www.youtube.com/watch?v=hvYLQM_fMMw
There are tons of "core" bands out there... The newest genre which stems from hardcore, to "screamo", steals from metal and rap and pop and turns it into one big ugly stupid sounding mess is.... Crunkcore... Yes... It exist:
(warning VERY explicit content)
http://www.youtube.com/watch?v=Zbg6lwq5yS4&feature=relmfu
You can thank hollywood undead for this...
None of the above guys should be given any affiliation with metal, It's not... It's connected to Hard rock
Metal on the other hand... Im not gonna try and break down the genres, but I'll offer you a sample of what I like, and some examples of some good songs with good growls and screams....
(The main point of this amazingly long and off mostly off topic post)
Lacuna Coil. Gothic metal band from Italy who also does hard rock and does an excellent job at blending the two styles. Gothic metal is, despite being called "Gothic" quite less grim and more melodic than other forms of metal, usually featuring mostly clean vocals and two lead vocalist, both mail and female.
I would love to see these guys in concert at busch, they make tons of poppy songs and general rock songs and all their content Is family appropriate(well everything I've heard from them anyway, they got alot of music out):
http://www.youtube.com/watch?v=Ly9E30Hc5pg
http://www.youtube.com/watch?v=E8ucKaYr7h4&feature=related
http://www.youtube.com/watch?v=ubg_MgkIjvk
Opeth:
Considered metal Gods, these guys use an assortment of tactics and song styles, but they are overall metal. They dont use blatant idiotic screaming for no reason, rather they use it to evoke certain emotions in certain songs:
Now this isnt the most extreme metal song, but showcases how a MATURE metal band handles screaming, and highlights why I dont really take kindly to people calling metal outright screaming crap or w/e:
http://www.youtube.com/watch?v=AY5LRReFYus
<sarcasm>
Can you believe it, this song is by the same band! :</sarcasm>
http://www.youtube.com/watch?v=G3e6G_YNO0Y
Industrial Metal:
Now the video I used as my example for this is by one of my favorite bands and ultimately the video that got me into them... scared the crap outta me the first time i saw it.
But anyways I also think these guys highlight how someone screaming in a song doesnt kill it, ruin it or mean they suck, or are dumb. Most metal acts(ones I respect anyway) dont use it as a gimmick to say "look how cool we are" but rather add it tastefully throughout their songs:
http://www.youtube.com/watch?v=nghUCS6zqIE