Lame-metal is simply metal made by 'musicians' for the sole purpose of being metal. There is often little or no emotion or message shown in each song, other than the fact that they want to be known as people who don't give any fucks and hate the world.
HOWEVER, there are good bands consisting of members who; 1) actually don't give any fucks, or 2) do hate the world.
The difference is that when properly used, these characteristics can be used as inspiration for an artist; but when a regular Joe gets the same thoughts with all his friends and they want to make music about it, they use no effort. No matter how good it sounds, they just want to say that they actually did something with their lives (lol).
Lame-metal bands are usually just douchebags trying to get chicks, and play shows as often as they can, starting as soon as they form. By flaunting whatever fashion they think will get them the most attention, performing 'breakdowns' that aren't at all musical, and screaming and acting reckless in general to show their aggression, they earn the title of Lame-metal.
There are also Lame-metal bands with older members, but they're mostly just drunks paying homage to Pantera, or something along those lines. Usually only seen in bars, these bands are harmless to the music world, and actually somewhat beneficial (to the other drunks in the bar watching them).
Lame-metal bands almost never record albums; the ones that do are rich motherfuckers that get their parents to pay for it.
Andre: Hey man, I'm going home to listen to my new Diabolical Masquerade CD, wanna come?
Kevin: Nah dude, there's a Bring Me The Horizon concert tonight, aren't you going? There's gonna be a bunch of chicks, and the band is dressing up like Gumby characters, it's gonna be so BRUTAL!!
Andre: Uh... That's lame-metal man, never speak to me again. *cough cough* I mean, shit, I have stuff to do, bring some extra chicks home with you and call me when you get back.