Okay, a lot of wrong definitions here, most of which are just opinion rather than stating what System of a Down actually are. Here, I'll write a real definition (with my extra opinion, of course), rather than just saying "omfgz dey r da bezt!!!11" with no intelligent information or input whatsoever.
System of a Down are an experimental alt-metal/alt-rock band (no, they are NOT pop or nu-metal, before you start calling them nu-metal learn what the genre actually means) from Los Angles, California. They formed in 1995 and have released five studio albums to date. Some people are saying they're from Armenia, some people are saying that they're not. Let me get this straight... Serj (lead singer) and John (drummer) were both born in Lebanon. Shavo (bassist) was born in Yerevan, Armenia. Daron (guitarist) was born in Hollywood. Although, all band members ARE OF ARMENIAN ANCESTRY. They combine some middle-eastern elements in their music, also drawing influences from jazz, folk, blues and industrial.
Now for my personal opinion. System are an amazing band, and my favourite right now. I've been listening to them for nearly a year, maybe a bit longer. Although maybe in a few months time they might not be my favourite band anymore, they'll still be pretty damn great no matter how many times I listen to them. Yes, they've got a bit of commercial success. So what. When I first started listening to them I had no idea that they were popular. I'm fed up of hearing "they're popular, therefore they can't be good". That's bullshit. It's exactly the kind of crap you hear from small minded music snobs.
What also annoys me to no end are the stupid poser kids running around claiming to be their "#1 fan", whereas most likely they've only heard Chop Suey or BYOB. Good songs yes, but as a matter of fact, they have much, much better songs. If you're into heavier stuff (than say, Toxicity) listen to some of their self-titled album. One of the best albums ever created. And before you call yourself a fan listen to at least a few tracks off of each album (which, by the way, are all awesome).
(1998) System of a Down
(2003) Steal This Album!
Also, yes, some songs do have silly lyrics (Fuck the System, Vicinity of Obscenity, etc), which I personally have no problem with. But if you don't like it, don't judge them so quickly. Check out the lyrics for deeper songs such as Spiders, Mind, Aerials, Highway Song to name a few. Pure poetry. What I'm trying to say is don't judge System by the songs you heard on MTV or whatever. Listen to their less popular stuff then see what you think. Peace.
The purest forms of life,
Our days are never coming back...
~Highway Song (Steal This Album!, 2003)
System of a Down are definitely among the greatest, most intelligent and original bands ever.
An extremely amazing and underrated black/folk metal band from Norway.
Formed in 1995 and still going.
Just recently released an acoustic album entitled Origin, which is also great.
All black metal fans go check them out. Now!
(1997) The Olden Domain
(1998) The Archaic Course
Hardly anyone's even heard of Borknagar.
Awesome alt-rock band, fronted by Gavin Rossdale (formerly from the band Bush).
Currently have one album entitled Distort Yourself, released in 2005.
Come on through, come on over
You better not run or they shoot you down
And they're over this town
(Come On Over)
Institute are a great band.