That is a loaded question. The answer really is, great monitors will sound great, fully detailed, perhaps revealing every flaw, but also providing full dynamics at the full frequency range. Home speakers and many studio monitors will sound muffled, and sometimes either bright or boomy depending on how the manufacturer likes to promote their products.
I have tested many so called professional studio monitors and they are anything but flat and accurate. KRK, Mackie, and Dynaudio seem to be the worst offenders. The former offer almost no midrange detail, preferring muddy heft as a replacement, and Dynaudio seems to think bass is all we need to hear.
Mastering engineers do not use studio monitors, they use high end "audiophile" speakers systems with clean amplification. Most of those systems use drivers by Scanspeak, Seas, or Focal which provide exceptional detail, and if designed right, a razor flat frequency response.