I'm in the process of replacing hardware on my guitar, and so I heard that the kind of metal that the bridge and tailpiece on a guitar is made out of can affect the sustain and/or tone of the guitar.

Is this true?? If so, what metal will do what to sustain and tone, and how significant is the difference??

Also, if you were to change the bridge and/or tailpiece of your guitar, which manufacturer would you them buy from, and why??
Id get Tonepros hardware. Alot of artists use em, and they are probably the best manufacturer of bridges. Make sure you get locking studs too.
I've heard good things about tonepros. But I know that they're quite pricey and I've heard some say that they're not worth the money, or that they're not really all they're hyped up to be. What makes them so good??
There are two schools of thought on this.. some say go with light hardware, and make sure it's bolted tight to the body.. like on a Les Paul, you'd really crank the stop tail piece down to the body, and get something like a TonePros bridge that clamps down to the posts.

I say get heavy hardware and bolt it tight on LP style stuff.

With trem setups like on a Strat.. make sure your trem block is big and heavy. Wussy @ss tremblocks rob tone and sustain.

The ultimate goal for sustain is to have the string vibrate for as long as possible after it's plucked. To do that, you want to minimize the amount of energy that is transferred away from the string.

If your bridge or body is vibrating, it's that much less sustain you'll have.. which is why heavy guitars with fixed bridges and short scale lengths generally have better sustain.
What's the difference between the light hardware and the heavy hardware?? And what kind of material is recommended for either?

Could you also elaborate on what you mean by fixed bridges and scale length?? Is scale length referred to as the guitar scale??
^It's not that there's a difference, it's just two different schools of thought. As in, light, light aluminum, versus heavy brass, or something. A lot of people swear by zinc.

Fixed bridge is a hardtail bridge. Or a TOM. Basically, something that is NOT a trem bridge.
And scale length refers to the guitar's scale length. The distance from the nut to the bridge. For example, a Strat has a scale length of 25.5" whereas a Gibson Les Paul has a 24.75".
Aaah ok thanks for clearing that up. But do any of you guys think that TonePro's are all they're cracked up to be?? I mean what makes them so incredible?
I think that if your guitar is constructed well, and the bridge doesn't have any slack on the posts, then getting TonePros probably won't improve your sustain. They probably do transfer sustain better - but if your guitar doesn't need the bridge to tighten down on the posts to prevent slack, then TonePros wouldn't be a significant improvement.