
They’re still theories. Scientific theories are explanations of natural phenomena. Comparing a scientific theory to a scientific law doesn’t even make sense. Laws explain what happens whereas theories explain how something happens. Gravitation is a law explained by the theory of general relativity. Electromagnetism is a law explained by quantum field theory.
The problem is that that 3 of the 4 fundamental forces of nature are explained by quantum theory. Gravity is the odd one out. The best theory we have for gravity is general relativity, but general relativity fails at quantum scales. M-theory is a theory of quantum gravity. Basically, gravity is an extraordinarily weak force compared to the other forces. The theory posits that the graviton (force carrier of gravity) “leaks” out into other dimensions unlike the other 3 forces.