Have you seen the video above
? If not, take a look now because it will help you as you go along in this instructable.
A typical resistance Spot-Welder can range in price from about $200-$800, but with a little resourcefulness, and a bit of free time, you can make one like this for about $10 or less.
Spot welders are used to fuse thin sheets of metal together. They are most likely used in the auto industry, as well as HVAC for welding metal ducting.
There are a couple of videos you should see before starting on this project, because you may want some background on how the device works.
Here is how to: Make The Metal Melter
Here is what it can do: The Metal Melter