Cacti can flower? Most certainly. Cacti are plants. Somewhere along the way, plants need to procreate, to spread their kind, to stash away replicas of themselves and to ensure the continuity of their species. Flowering is the most common way in the plant kingdom, and to most cacti they are the way to go.
What do cacti blooms look like? As lethal as their thorns? Far from it. They're prettier than most actually. It's hard to believe a species so deadly can have some of the most beautiful blooms. Maybe that's what the thorns are for. I bet you somewhere someone already knows. One day he will find me and tell me why. Enjoy.