Fontina is an Italian, semi-firm cheese made from cow's milk. There are American versions of fontina; however, true fontina will have an orange-brown rind. It is typically rich and creamy with a nutty taste. Thus, other semi-firm cheeses with a buttery, nutty flavour can be used in place of fontina.
Emmental is a Bavarian cow's milk cheese with a mild, nutty flavour. It is known for being an excellent melting cheese, which is why it's commonly found in fondue. Emmental is a Swiss-style cheese with characteristic holes throughout.
Gruyere is a Swiss cow's milk cheese, often used in gratins and fondues. Gruyere has a nutty, slightly sweet taste and can range from semi-firm to firm. Some Gruyere is cave-aged, giving it earthy, mushroom-like notes. Gruyere that is aged less than six months is closer in texture to fontina.
Provolone is a southern Italian cow's milk cheese with a semi-firm texture and a slightly smoky taste. Provolone is either dolce or piccante. Dolce provolone is sweeter and softer, while piccante is semi-hard with a nuttier flavour. Piccante-style provolone is a better substitute for fontina than dolce.
Gouda is a Dutch cow's milk cheese which is commonly aged for three weeks to a year. It typically has a yellow wax rind and is round in shape. Gouda has a mild, nutty flavour and tiny holes throughout. It melts well and makes an excellent substitute for fontina.