Metal reflects microwaves and builds up electric charge on its edges and points. That is what you see as sparks, and it can damage the oven or start a fire.
A spoon or fork has points and edges, which is exactly where the charge concentrates. The result is arcing, a bright flash and crackle that can scorch the cavity and in a bad case start a fire. Smooth, thin metal such as foil is also a risk, though some makers allow small, shaped pieces in specific ways.
| Short answer | No |
|---|---|
| Why | Microwaves induce charge on metal edges and points, which arcs |
| Worst cases | Forks, twist ties, metal-trimmed plates and crumpled foil |
| Real damage | Scorched cavity, burned plates, damage to the oven |
| Safe alternative | Glass, ceramic or plastic labelled microwave safe |
What to do if you already put metal in
- Stop the microwave straight away. Do not wait for it to finish.
- Open the door only once the sparking has stopped, and remove the item with care since it may be hot.
- Look inside for scorch marks on the walls and the waveguide cover at the side or top.
- Check the item and the oven for damage, and stop using the microwave if it is scorched or still sparks.
- Wipe the cavity once it has cooled.
What happens when you get it wrong
- Fire. Arcing near paper, food or plastic can ignite them.
- Damaged oven. The walls and the cover over the waveguide can burn or pit, and repeated arcing can damage the microwave source.
- Ruined plates. Metal trim and decoration burn off or crack the ceramic.
Remove the spoon and use a microwave safe bowl or mug. A plastic or wooden utensil is fine for stirring.
A glass or ceramic dish for anything that needs a spoon standing in it.
Frequently asked questions
Why do forks spark in the microwave?
Charge builds on the tines and the gaps between them, which jump as small arcs.
Can you leave a metal spoon in a mug in the microwave?
It is not recommended. Some people do with no result, but the points can arc, and manufacturers advise against metal.
Is it safe to use the microwave after it sparked?
If there is no visible scorching and it still heats, it is likely fine, but replace it if it is damaged or arcs again with nothing metal in it.
Can you put foil in the microwave?
Only in small, smooth pieces and only if your manual allows it. See the foil page.