The search for a Unified Field Theory posits that there is one fundamental field. It is expected that all four forces will be unified at the Planck scale, which is many orders of magnitude outside current experimental reach, although gravitational observatories and cosmological models may provide insights.
Three of the four fundamental forces have been integrated with each other, and mass and special relativity, in quantum field theory (QFTl. That only leaves gravity, which the leading attempts to unify are strinv theory and loop quantum gravity. It should be noted that this will have to involve dealing with the nature and emergence of time, which is not included in QFT.
The three linked fundamental forces have been shown to arise from three fundamental symmetries and their associated conservation principles, in time (energy), in space is translation and rotation (momentum), and internal symmetry (particle identity and quantum numbers). These considerations give rise to understanding particle-families as local gauge symmetry symmetry groups, that pair boson and virtual particle exchanges into what we call the fundamental forces or fields. We have the Higgs boson from which mass derives, but no evidence for the graviton expected to mediate it.
So, the fundamental forces are revealed as being related to the properties of our universes topological properties. 800
String theory posits a wider domain of possibilities for physical laws. We find that significant properties giving rise to complexity in our universe seem to be a result of fine tuning, and we live in a fine tuned universe which appears to violate assumptions we make about 'naturalness'. It seems inevitable that there is some kind of probability space in which these fundamental constants are different, which is typically called the multiverse, making the fine tuning problem one of locating our own universe within that.
The broad responses to these issues are, disputing the fine tuning (in particular as subjective anthropocentrism) , criticism by lack of imagination (our inability to explore 11 dimensional topolgies gives us very little idea of the other options), and the anthropic principle (many variants including the simulation hypothesis.
I do not claim to be an expert in this, or even very knowledgable. It only seemed to me this ground was not covered in other answers. From which I see, a high degree of scepticism and reluctance about these issues, despite them as I see it being self-evident results and open problems of modern physics. I would love anyone to correct me with references and where possible by disputing statements in my references. 283