Guitar Tone Setup

I am having a bit of difficulty getting the right kind of tone from my
guitar and setup. I am looking for a heavy distortion sound similar to
Metallica, but being able to switch to clean and it sounding good.
I have an Explorer with 2 EMG 81 active humbuckers fitted, a Boss MT-2
distortion pedal, a Boss CS-3 compression pedal, and use Marshall amps of
varying ampage.
I cannot seem to get a good distortion sound, it it either one extreme or
the other. Can you give some advice as to what I need to do to get it
somewhere near right.
Also when I turn the gain up, the guitar squeals and gives a lot of
feedback, again I cannot seem to resolves this, and I dont know how!
As you can imagine this is quite frustrating, any help would be
appreciated.

[font=trebuchet ms]I find I get my best tones by tweaking my sounds clean first. Then I push the amp to where its just starting to distort. Then use just enough overdrive or whatever to push it over the top. The days of just reefing all the knobs to 11 are long gone, and truth be told, it didn't sound good then either.[/font]

go to the boss website get to the metal zone page and they will show you where to set yer levels on the pedal for 70's rock, fat metal,thrash metal....check out a noise suppressor pedal..

It looks like you have some good advice here above. I am just wondering if you have setup your guitar to compressor to MT-2 and then to Marshall amp. If so you may want to start as per previous advise get a clean sound first, switch your compressor on, run up attack until there is some compressoin going on say 2:1 as a start (Remember bass usually needs more to stop erroneous harmonics and boomy sound in poor acoustically controlled venues or they funk on everything high compression lots of slap) Now allow about 50% sustain again to start with. With MT-2 OFF you will not notice much, but lets leave it there for a minute. Now go to your amp and drive the channels so you have a warm sound YOU LIKE!! just before an overdrive sound is noticeable and leave amp alone at that position for a minute, back to MT-2 switch on from zero drive, adjust tone so it matches in a "Switch-on switch-off" mode drive the MT-2 until the amp starts working harder and a noticeable overdrive is apparent when playing (oh to make it simple have guitar volume at full). If you get squeel very quickly then there is a problem either batteries guitar actives on pickup, batteries in MT-2 or faulty MT-2 or C/E pedal. If you get a great sound then keep adjusting IN SMALL amounts. remember feedback is sometimes desirable in a controlled fashion this includes distance from amp which way you are facing and your playing technique...most important. If everything is ok play around with the three variables in two pedals and amp always leaving guitar at full volume ...why full volume is the nature "tone" state of the guitar as is treble or bass controls to full 100% position Remember pickup choice for solo or power chords may be a factor as well.