I have searched the board here and found lots of info on machine applique but very little about the thread to use. One member said to use fine applique thread> I went to LQS and Joanns and neither have anything called applique thread. Just cotton, silk, embrodiery thread and all purpose. Also, how do you tell the threads weight/ Thanks in advance for your help.

Depending on the look that I am going for, determines my thread choice. If it's an old fashioned looking quilt, I use black, white, or cream cotton.
I love to use the rayon embroidery thread on the top, and a matching polyester cotton in the bobbin, on the girls "cute" quilts.

I use regular Connecting Threads thread because I want my applique stitches to be seen. If you want less visible then try the embroidery or poly thread. I'm sure you'll get more ideas to think about. :)

I use Sulky or Madira 40 wt. rayon thread for most everything.
And it's very important to use embroidery needles.

A fine thread would be a 60wt. Mettler makes a cotton 60wt. Superior Masterpiece is a 60wt. cotton. Some use a clear monofiliment or polyester clear thread, especially if your machine doesn't have the kind of stitch that you want to show.
You might want to do a practice piece and try a few different threads.

i use silk, invisible thread, or cotton depending if i want the stitching to show.

I use Isacord thread for EVERTHING!

Thank you all for your help.