Kripes man, I've played slap Black Sabbath. Slap is not FUNKY by itself, BUT it lets you time and pulse the song while you play riffs or a melody, that what slap does, its allows you to funkify ANYTHING.
EG, I dont dig shred, not hate, but jsut cant hear much musicality, but, as long as there is a drum groove, I can hear slap lines to the bass parts. Even simple things like plucking on the snare beat, double tumbing the kick drum, etc.
Some metal doesnt not have a pulse, which I would define as a "syncopated rhythm". Its harder to provide a slap bass line , which incorporates the pulse of the song, if the song is Soul less". Slap , done PROPERLY ( and it often is NOT),
You boys post up an metal mpeg with some syncopated rhythm, and I'll slap it silly.
The metal I cut my chops on is early Sabbath ( I started playing in '70). I can through proper slap riffs into most of those tunes, and some I can slap every bar.
I particularly like slapping the bass solo " Basically"
Aw Geezer would be proud. Its VERY musical.
Use your imaginations. Start with a "pulse", a rhythmic pulse. Start playing that pulse on your bass, ghosting (muting) it. Just feel it, the pulse and then let the melody come to your open mind. Your drummer should accent the pulse on the slap line.
Metal is only harder since, 1.) the bpm is usually north of 100, and 2.) often straight time w/o syncopated time accents. You gotta make your own man!
lesson5 sabbathbassicallybackslap.wav - 3.31MB
There's an old lesson. Its the only file not in th e .aud format. Sounds like a 10 yr old, yup I know. Time is, I guess south of 80, maybe 65 bpm, way slowed down. Wasnt labled and time wanders, yes I know...but think of every articulation of the bass along with a crash, pop or kick on a drum kit, speed it up to 100-120 bpm ( ++ once you're good enough), as a backdrop to where the guitar stops "chunking" and takes off on high to a "searing" solo riff.
( guess yall know what a terrible player I am now)

)
Another area where slap would work MINT in metal is in very fast passages. One of the most beautiful mechancial aspects of Vic Wooten's slap ( at the top of the game, iner alia) is the near 300 bpm articulations you can pull off between hammer ons, plucks thumps and flcks.
Now, when you do all that on a bass you LOSE that hard driving 4/4 pulse of most metal ( I;m ignornat on metal, so pardone my attemps here ) , so the drummer REALLY has to step up and either more heavily suppsoer the background 4/4 pulse OR competely fall into the same patterns your playing.
So , to sum. Good slap bass articulates the pulse of a tune, uisng ghosting thumb/plucks , and kinda always has that running in the background between runs. In the context of metal, the drums have to be wired into that pulse, to either step along side it and support simple time without stepping in it, or envelope tehmselves into the pluse froming a drum/bass lines that would effing SCARE msot metal heads as it resonated their backbones down to their chi.
Sooooooo GET ON IT mullet..... craft some slap metall that will make me listen to , adn appreciate, metal again.
You guys you tube DOUG JOHNS use " buzzjohns ". A couple of lessons you'll find. Doug should be having this discussion, not me. Check him out. Bet Doug would know exactly how to make metal slap scream. I'll see if I can link you to a "heavy" tune of Dougs.
Peace. Out.