metal heats up in a microwave but if your gaps in the links of the mesh are small enough (1mm), it could work. the microwave mesh works because it has supper small gaps between links, which stops the microwaves, which have bigger wavelengths than the gaps. That's like trying to put something big in something that cant hold it, or lets say a trying to put a couch in your car trunk. If your mesh is too thick though, it could cause sparking and burning of the mesh. Even if you find a perfect mesh, it will still heat your food up through absorption of the microwaves, if not, it will heat it up through reflection or letting a couple microwaves through accidentaly, and even if those don't heat your salad up, the surrounding foods and entropy will. If you want to learn more though, the mesh is called a Faraday cage and its really cool. But, answering your question, to be safe, just pay more attention to what your putting on your plate and you should be good.