The best milk to use for foaming is whole milk. Whole milk produces the most stable foam, giving the best flavour and texture.
Non-fat or low-fat milks may produce a thinner foam due to their lower fat content, but can still be used for frothing and steaming if desired.
Almond, coconut and soy milks will not produce froth as well as regular cow’s milk but can also be used in specialty drinks like lattes or cappuccinos.