jealousy in a relationship, is it flattering ? annoying ? unnecessary ?

we've all been there..that point of dating when your partner becomes enraged with jealousy..is innocent flirting enough to set them off is it wrong ? is sex that strong to send some one into a crazy fit ? isnt it normal for ppl to naturally flirt ? i think if u love someone and u trust them there shouldnt be any extra messy drama. If youre dating someone attractive it kinda comes with the package lol so again, is jealousy an excepted thing ?