Metal Ingots are a fairly easy to produce resource in Ark. They are produced in the Refining Forge and are used in a number of crafting projects.
You'll need a Refining Forge to craft or refine Metal Ore into Metal Ingots. Once you have the Refining Forge it's a simple matter of throwing your Metal Ore in and adding some Wood. Then just light the fire. You can also use Thatch or Sparkpowder to fuel the Refining Forge. Using Wood will also produce Sparkpowder.
Now comes the interesting part. It takes 2 Metal Ore to create 1 Metal Ingot. And you'll probably need a ton of Metal Ingots. Check out these pages for details on harvesting Metal Ore quickly and easily:
Wood & Harvesting
Metal Ore & Harvesting