I found this explanation here: Food that sticks is caused by chemical bonds that form between the food and the material of the pan - almost always a metal. These bonds may be relatively weak van der Waals forces or covalent bonds. Protein-rich foods are particularly prone to sticking because the proteins can form complexes with metal atoms, such as iron, in the pan. But what it does not explain is that food does not stick to a pan when cold, but it does when hot. That's what I want to know. Here's my guess. It's the same reason why you need heat to take two helium and make Beryllium. Heat increases the odds of two helium sticking together because there is more motion and hence more probabilistic resources. When food gets heated the atoms move more and there is a greater chance of the atoms from the food and the metal coming nearer each other and forming a covalent or Van der Waals bond. let me know if this is correct.