Scrap Metal (Fallout 3)

Scrap Metal can be traded to various different NPCs located in Fallout 3.

Walter in Megaton
Scrap Metal is desired by Walter in Megaton after completing the unmarked quest: Treatment.

He is located in the Water Purification shack during the day. He will pay 10 caps for every piece of scrap metal the player brings him (rewarded 5 XP per for each piece as well). For many players (especially those who reside in Megaton) Walter may be the most preferable option (even when XP is no longer an issue) as you can easily fast travel to Megaton to unload your stacks of scrap metal, and then head down the ramp to Craterside Supply to sell other unneeded loot.

You may also just give the scrap metal for free to Walter for positive karma. This is a good way of increasing your karma, given how common scrap metal is.

Winthrop in Underworld
Winthrop in Underworld also trades for scrap metal. He will give 1 Stimpak, Rad-X, or Rad Away for every 5 pieces of scrap brought to him.

Unless you think you're making a difference, selling scrap here is not as profitable as other scrap buyers. For instance, selling to Walter in Megaton will net you 10 caps each; Stimpaks cost generally about 30 caps. Also Casdin will give you 1 Stimpack for 2 pieces scrap metal. By selling in underworld you lose profit if you were to trade the scrap metals for a Stimpak.

Although in times when these items are hard to find (by lack of traders selling them, lack of known traders, or by the player or having bought out all such items from those selling them) this can be a useful venture in a pinch.

Protector Casdin at Fort Independence
Protector Casdin of the Brotherhood Outcasts is located in Fort Independence. He will trade 12- 5.56mm rounds, 1 Stimpak, 1 Rad Away or 1 Frag Grenade for every 2 pieces of scrap brought to him.

Ammo Press at The Pitt
The Ammo Press in The Pitt is located in the Steel Mill. Scrap metal is very useful in the presses due to it yielding more ammo than scrap put in. For example, if one puts 500 pieces of scrap metal into the press to make Shotgun Shells, it will return 1500 shells.