"Did you really read the instruction manual?"
The Microwave Oven is an electric machine used to cook food stuffs at a higher speed than a normal furnace, and is NOT designed for metals.
Any attempt to use any metal Ingot, Plate, Block or Dust in the Microwave will result in a considerable explosion. Interestingly however, Rods, Rounds, Screws and Bolts can be cooked in the microwave, despite being metal. It is unknown whether this is actually a bug. Eggs will also explode the microwave, as warned on page 7 of the "Microwave Oven Manual" book, which says: "Do not insert eggs. Just don't."

Active Microwave

Inactive Microwave

Maximum Safe Input :
32 EU/p (LV)

Any furnace action takes 100EU, while a normal Automatic Furnace takes 400EU.

Possible Upgrades:

Overclocker
Transformer
Battery
Minecraft Joules
Steam

Recipe:

6 Aluminium Plates
1 Lead Plate
1 Magnetizer