I'm sure there's a rule about it but I use what my machine likes best and gives me the best results. So far my machine likes aurifil, Connecting Threads cottons and polyesters, metallic embroidery thread by BFCreations. And just now finished a friend's quilt using Glide thread. Broke only once and I'm sure it was because i did something stupid and not the machine's fault. I know not to use serger threads or that's what I've been told not to use.