What's the main difference between "thaw" and "melt"? Are they interchangeable in this context?

Native speaker’s answer
Rebecca
Ah, so "melt" refers to something frozen going from a solid into a liquid. "Thaw" is the process of something defrosting and doesn't always refer to a liquid. For example, when you defrost meat, it "thaws". It doesn't "melt". In this case, "have your face melted" refers to something slightly different! It refers to the heat of the chilis or spiciness of the food- it's similar to how heat "melts" metal. Because of the heat, it'll feel like their face is melting. Ex: This food will melt your face off. It's so spicy! Ex: My ice cream melted and made a mess. Ex: The rivers thawed over spring. Now we can go swimming! Ex: I'm waiting for the turkey to thaw before I cook it.