When we design our spacecraft, we cover the outside metal structure with thermal blankets composed of many layers of Mylar. The layers are spaced in such a way as to break up, and even vaporize, most of the high-speed particles smaller than about half a millimeter, so our key electronics and various propellant tanks are not harmed. Particles a bit larger than half a millimeter could still hit our spacecraft, but we rarely worry about particles larger than, say, a marble, as the chances are very low of ever running into one of them.
NASA, ESA, J. Parker (Southwest Research Institute), and L. McFadden (Univ. of Maryland)