You are not going to be entirely satisfied with your sound if you just get an effects pedal but don't ahve an amp that is capable of those heavy sounds. While something like a Metal Zone is good, it's not going to make you sound like Megadeth. As you can see here: http://home.iprimus.com.au/mccormac/equipments.html bands like Metallica and Megadeth rely on powerful amps; noatably Mesa Boogies and Marshalls (two brands you will see crop up in this area) rather than effects boxes. This is not particularly practical for home playing - though note the use of power attenuators that can help keep the volume down -, but I am merely warning you that although effects can sound cool, you're not going to sound like you might want without spending a hell of a lot of money and having a massive area in which to play.