I would think that through, and probably call the 800 number on the
can. First, if it is from Rustoleum, make sure it is not one of their
products specifically made for metal. They use different formulas for
metal specific products and general primer.
I put latex over oil based primer such as Kilz, Zinser, Krylon, etc.,
all the time and prefer it to the latex primers for the most part. But
never over the primer specifically made for metal. YMMV.
But why take a chance? Primer is cheap. You can buy a gallon can of
oil base Zinser for something like $14 and a quart for $8. As much as
some people hate to paint, I would just buy the primer I knew without
doubt would work and be done with it.