Is what comes in a dream the real Angel of Death or merely a dream?

Seeing angels in a dream is permissible for those other than prophets. It is reported in Sahih al-Bukhari and Muslim that Ibn Umar saw two angels who took him to the Fire, then another angel met him, and the Prophet, peace and blessings be upon him, affirmed this vision. What indicates that they were angels is that they were mentioned with goodness, or that they were informed of it, or by the Prophet's affirmation, peace and blessings be upon him.

However, it is not possible to conclusively determine that what the sleeper sees is the angel itself or its true form, because revelation has ceased, and the true natures of angels are not known except through revelation. This vision may be a glad tiding or a warning.