A microwave is the other appliance named for melting cheese on loaded nachos.
Loaded nachos may be placed in a microwave to melt the cheese after tortilla chips, meat, and bean toppings have been arranged on a platter. Microwave heating is a quick alternative to broiling, making it common for home preparation and for reheating assembled nachos.
Microwaves heat food by exciting polar molecules, especially water, throughout the food rather than relying only on heat from the surface. Cheese softens and melts rapidly, but the result differs from broiling: a microwave generally does not brown the cheese because browning requires high surface temperatures and drying. The chips can also lose some crispness if moisture from the toppings builds up.
For that reason, cooks often add lettuce, tomatoes, salsa, and jalapeños after the cheese has melted. This preserves the contrast between hot cheese and cool toppings. A microwave is not the only possible method in everyday cooking, but it is the second appliance specifically named in Wikipedia’s description of loaded nachos, alongside the broiler.