I read some of one of the papers listed on the wikipedia page.
The basic idea seems to be that one might explain the strong force(this idea is from before QCD was established) as being a consequence of a spin-2 particle (which is not the gravition!) that has a coupling constant such that it becomes strong at the right energy scale. Didn't read much more but i think the idea is that hadrons might be microscopic black holes that interact not via gravitons but via this other spin-2 particle. So there would actually be two metrics, two Einstein-Hilbert terms for each metric in the action but with different coupling constants.
I'm pretty sure the idea didn't work out. But maybe it is of some historical interest especially if low scale QG models have something to do with nature and we see black holes at the LHC.