Re: Good Death Metal/Heavy Metal pedal?
If you plan on getting a better amp eventually, then I would advise you save up for it and just get it too. There is a good chance that all that will happen if you spend 100 on a distortion pedal right now is that you will eventually get the money for a better amp, then your pedal won't help you much and chances are you will either give it away, keep it but forget about it, or sell it for chump change. Then at the end of the day you ended up spending more money than you needed to. So in order to prevent this from happening, you gotta choose wisely, maybe even considering spending a little more on a pedal so you have one that will still be of use to you when you start to acquire new gear.
I wouldn't be saying this if it didn't happen to me. There were so many times where I wish I could get the money back I spent on the pedal to just put towards the amp so I could get it quicker, even if it was only $100. While the cheap distortion pedal could make a cheap little amp sound acceptable it can cripple the sound of the more decent amplifiers, so you might not ever use it again after you get the better amp unless you modify it, and even then other stock pedals can catch your eye that do the job better that you would probably want. Then after it is modified, it actually drives the value down of the pedal so you have a harder time selling it if you decide to as well. This can be prevented by buying a decent amp first or getting a versatile and worthwhile distortion pedal to keep around, even if it means spending a little extra. If you check out the rigs of your favorite artists, you would probably see that most of them don't use high gain distortion pedals, but probably little overdrive or boost pedals while they prefer to get the gain pumping from their amp. This is a popular choice because it keeps your distortion dynamic and responsive to your playing style instead of clipping the signal too much before it hits the amplifier and makes everything sound to fizzy or flat. So you should choose a pedal that has a good "midrange" (not to be confused with EQ) of distortion qualities and flexibility, while at the same time having enough distortion capabilities on tap to satisfy you now. That way the pedal you get will still be of use to you in the future and you get the most out of your money.
That is just my side of the story because I have been exactly where you are now. However, I am not totally aware of your financial status and what you plan to do with your guitar playing in the future so in the case of distortion pedals that would work for you:
Boss- Power Stack

Ibanez- Sonic Distortion

VOX- Satriani Satchurator
I chose these because they crank out good amounts of gain, are pretty versatile on their own but geared towards heavier metal, work great with a good amount of amps, are slightly under or at $100 and can be found for even less expensive used, retain their value well enough, will come in handy in the future, and are all modifiable with relative ease if you choose to do so later on.