Metallic asteroids have already been identified from remote sensing: 1986 DA; Psyche & Kleopatra are three bodies which seem to consist of pure metal. The most likely explanation of these asteroids is that they are formed from metallic cores of larger objects now defunct; but there are other explanations as well.

The SF fantasy of dust proving an insolvable obstacle to asteroidal activity wasn't supported during the NEAR/Eros landing & may not be an issue at all; for reasons which are currently unclear. The behaviour of particulate matter in the electromagnetic vaccuum of solar orbit needs to be tested; & MUSES-C will be a good first step.

Robert