كَأَنَّ الْقَمَرَ مِصْبَاحٌ
Translation: The moon is as though a lamp.
«كَأَنَّ»: particle of comparison and accusative government; «الْقَمَرَ»: accusative ism; «مِصْبَاحٌ»: nominative khabar.
The particle changes the meaning to comparison, not the underlying case pattern.