Re: best pedal for heavy metal / pedal
Heavy metal is a very ranged notion of sound which goes from a not so distorted tone with watts and body to a fuzzed out often notched mids buzz out.
Seemed to be a trend for a time to deeply notch out the mids with massive gain and while that does have a tone, problems arise when trying to use that in a band. The guitar itself is a midrange instrument and without mids you cannot cut through the mix or even seem to fit within the sonic area where you should be that is open for the guitar. Super high gain gets washed out in a band like a wall of effects you will not hear all the fancy over processed sounds. Ever listen to a lot of "metal" bands live their sound is rather weak and fizzy. Helps if you have a versed sonic engineering tech to make sure the EQ is properly done, plug and play, no thought to anything, seldom yields anything other than dumb luck.
Mesa came up with the low mids notch cut at 750hz which leaves the area around 1k for the natural sound of the guitar. If you can adjust to notch around there it sounds better. If you notch wrong you and literally remove the core tone and sound of the guitar itself. A lot of demos out there demonstrate this.
Personally I feel you need a closed back cab, I prefer a 4x12 myself for the body and power. Trying to get metal tones on an open back 1 12" is going to sound a little thin and nasal.
Contrary to popular yada, wattage is not loudness, wattage is headroom and fidelity, there is no low end without wattage. Metal can be very thin and nasal with no bottom end punch and just not a very good tone. Early Sabbath is really not that distorted and early Priest used Marshall bass amps they they went for cool tones with their gain structure. Removing the wattage out of amp is not about making it less loud more so than castrating it. Loudness as a function of measure sonic physics is defined at a mere +3db increase for every doubling of wattage. A low amp can be really loud but the depth of the sound is not there. A 20 watt amp is in potential +3db louder than a 10watt. A 40watt +3bd louder than a 20watt. So yeah things do get louder with wattage but there is a whole lot more involved than just loud.
Speaking from my personal use/ownership, the best high gain pedals I have used or still have:
Wampler Triple Wreck (Might be the most intense but still articulate high gain, not very versatile but dials in EQ for that monster Rec tone, boost is actually a fuzz circuit laid over the distortion which is OK for single lines gets a little muddy on chords w the boost. This was a fav for a period of time until I got the itch and wanted to try something different.)
Wampler Pinnacle Deluxe (Remains on my board as a go to pedal, I use it on lower gain vintage mode for a great Pagey sounding Marshall. Does the EVH "brownsound" amazingly. Wonderful range of adjust. I do not see myself ever dropping this pedal sounds so amp like and again all it how you learn to adjust the EQs, )
Seymour Duncan Palladium (my new jewel in the crown, others might muster more intense gain but this has articulation and real tube amp sounding high gain, works well with boost or drives in front as well.)
5150 EVH, I do not have but is a great pedal (There are many demos of this pedal and I have to say some great tones, for the price a real winner)
Mesa Throttle Box EQ, not very versatile sort of fuzz mixed into the high gain structure. (Intense super gain but for those who can handle or like a fuzz/distortion. Was not my thing despite I dig the Mesa Pedals.)
Boss Metal Zone w Keeley Mod (had this one some time back, tricky to dial in but once you learn the EQ can get some monster tones. I would say the Wampler Triple is the deal these days and a much better pedal. I was never a big fan of Boss to begin with. Most demos of this have just terrible EQ adjust on the pedal and it gets a lot of bad rap for that. It had one basic sound and when you get that perfect EQ setting this puppy cranks massive low end and strident high end. Was not a terrible pedal but did not have the articulation of many others.)
Black Arts Toneworks Coven (if you want just over the top fuzzed out distortion madness like Satan crapping a big muff, these guys make some vicious fuzz and distortion pedals.
I like my rig to be able to adjust and create a wide range of tones and sounds so I like a pedal like the Palladium which gives me that high gain tube amp thing but with better tone and articulation. I like hearing my guitar in the gain structure else it does not matter what you play. When you use a Les Paul you like to hear what makes it a Les Paul. The more you develop as a player the more you define and seek note articulation in the higher gains. High gain pedals and amps can be tremendous fun to play but not by far a fraction of what the guitar has to offer.