In beading when should you use wire to string beads or should you only use thread?

Well from personal experiences I use wire for when Im using heavy beads or many beads that can make the necklace or braclet heavy. I use fishing string for light weight projects. Also remember that the crimp bead can also cut string so be carefull, if you don't pull it could fall apart while putting it on or wearing it. Bead on, good luck. SELAH!!!