As know our Universe is expanding, which I have always visualised as some stretching of the metric of space-time, which "flattens" it. In the same time. our theoretical perception of Black Holes usually includes some kind of singularity (or at least some extreme curvature), bounded by an event horizon. Clearly, if my naive understanding for the expansion of the Universe is correct, then it would be a natural instrument that may potentially dissolve Black Holes, which I've never heard of before => it's probably wrong.
Thus, I'd like to ask for a clarification what the Expansion of the Universe actually does and how it affects Black Holes (and the curvature of space-time, in general)?