How does the electromagnetic force differ from the other three forces?

The is almost nothing similar between the electromagnetic (EM) force and either the strong or weak nuclear forces. About the only thing I can think of that links them is the fact that both are mediated by an exchange particle - the massless photon in the case of EM, as opposed to the gluon for strong force and the Z and W bosons for the weak force.

The strong force acts on quarks (and other particles composed of quarks) but not leptons (electrons for example), while the weak force acts on both quarks and leptons. EM force does not depend on the same properties of matter as these forces.

The two nuclear forces are both very short range forces, and are limited to the scale of the nucleus. EM force (like gravity) can extend its reach over practically infinite distances.

Gravity on the other hand shows many similarities to the EM force. Both are inverse-square forces, meaning the intensity of the force drops as the square of the distance between the interacting bodies.

Both are conservative forces and as a result can create potential energy when objects are relocated in the presence of these forces.

A difference exists in the property that a body must have if it is to experience these forces. For gravity, that property is called mass, but for EM force, it is electric charge. These are completely independent "fundamental properties" of matter (meaning we do not really know what causes them), so an object with charge does not necessarily experience gravity, and a charged body need not experience gravity.