Comment by sharpneli

It's not. Just like how if you push two identically charged plates towards eachother the potential energy in that system is not made of photons.

Sure you can describe the electric field in that case by a viewpoint where you sum virtual photons together to get said electric field. Whereas a non virtual photon is alltogether a different thing. You can actually describe a normal non virtual photon as a sum of virtual photons.

Point is that virtual particles are just a mathematical tool.

Actual real gluons do exist and they're analogous to the actual photon.

In case of electromagnetism the actual stuff is the electric field. With proton (so in quantum chromodynamics) it's the gluon field. It's called that because every particle has a field and every field a particle. It would be kinda like calling electric field a photon field. Same difference.