Knitting with wire Christmas card. Tub and Star cut from copper sheet.

The wire is 0.236mm gauge copper from an electrical supply shop. It is quite fine and very pliable - you can easily break it with your hands, so I was pretty sure I could use it on the machine. It knits very easily and feeds though the tension assembly perfectly.
I used a standard gauge machine and tension 8
Here is the pattern if you are interested:-

This is only a very simple shape but may get you started with wire.
Cast on 1 stitch by e wrap, leaving needle in HP
Put needle next to this one into HP on SAME side as carriage to increase, Knit 1 row
Repeat this increasing and knitting until you have a tree big enough to fit your card.
Mine is 21 rows and 21 stitches.
Knit the last row on tension 10 and remove by casting off with the latch tool (or do your normal cast off).
Pull the tree into shape - it will be a little squat. The loops formed by increasing on the same side lie neatly along the edges making the tree shape quite triangular.