The key to melty magic lies in a cheese’s balance of fat and moisture. While cheddar offers a delightfully sharp flavor, its high-fat content (around 35 grams per 100 grams) can lead to a more oily texture when melted.
This tendency is shared by many hard cheeses like Red Leicester and Double Gloucester.
So, the higher the fat content, the more oil you can expect a cheese to produce when it is melted.
Hopefully, you see where I’m going with this now.
The best types of cheese for melting will always be low in fat and high in moisture.
When you melt cheese like this it will initially steam and produce large bubbles.
Plus, it also helps if this type of cheese is quite elastic.
The large bubbles produced by low-fat, high-moisture cheese will break the surface of the oil initially produced by the melting process.