My internet went down a couple days ago, and I had this already typed out so I'm still going to post it and keep the debate alive.
Using something artificial in metal is kinda defeating the point of metal IMO...I like metal raw and aggressive, not all "oooo I need my kick drums to be perfectly clear oooo"
Still not taking sides on this though.
Getting the metal kick sound without triggers is easy. I'd assume the problem comes from either the drummer not knowing how to set up his kick and pedal to achieve it or the sound guy being unaware that that is what the drummer wants or is unfamiliar with the genre so doesn't even attempt to get that sound. Most kick drums today aren't helping the issue, you'd get a much better 'metal' kick sound out of a 20x14 or 22x14 kick than from a standard 22x18. Shallower depth drums respond quicker and require less power to play at decent volume too.
Instead of the coin trick you can use a metal patch - http://www.danmarpercussion.com/topsellers/DMKbg.gif
, it won't damage the head and with a wooden or plastic beater you'll be in click heaven. Keep the resonant head unported for more volume and low end, little bit of muffling, and permanently mount a suitable mic inside. Got a friend who has a condenser mic mounted in his kick, with an XLR jack drilled into the side. Easy set up at gigs and it sounds awesome.