At least for microwave ovens, with domestic models reaching 1 kW and commercial (e.g. in food) 2 kW, the shielding on these needs to be pretty darn good to make sure that someone standing right next to it doesn't get their body fried. The maximum allowed leakage power density is 5-10 mW/cm² [1], according to a 2004 study even then most ovens barely get up to 1% of the legally allowed emissions limits [2, page 7].

Out of random interest I tested the "put a phone in it and call it" and it didn't work (as did wifi) that's mentioned in [2].

[1] https://www.hea.de/fachwissen/mikrowellen/sicherheit

[2] https://www.sfu.ca/phys/346/121/resources/physics_of_microwa...