What a volcano would look like on a metal world

On Earth it rains water, on Titan liquid methane comes from the sky. On some planets it rains iron or even diamonds. Such differences also exist in volcanology. On Ceres, researchers have discovered ice volcanoes, while terrestrial volcanoes spew cinders of liquid rock. On the asteroid Psyche, which consists primarily of metal, there may once have been iron volcanoes. Perhaps elsewhere, too.

But what would such volcanoes look like? Knowing that is important for detecting them on distant celestia...