A question I am often asked by friends who want to try prick ‘n stitch card making is what thread do you use? The answer is Kreinik metallic 1 ply cord.
This is the thread I use to test stitch the patterns on the Stitching Cards web site. The pattern instructions list the colours of the Kreinik threads used. There are 26 colours in the range. You can see a colour chart of the metallic threads on the Kreinik web site. The cord section is quite near the bottom of the chart. Look in the column headed 1 ply.
The single colour threads are smooth and strong, which helps them stand up to the abrasive effect of the rough edges of the holes in the card. The thread keeps its tension very well, just what you need for sewing on card. The finished result has an attractive metallic sparkle and gives a sophisticated look in my opinion.
Some of the threads in the range are multi stranded. The antique threads are a combination of the base colour, such as silver, with a strand of black. The antique threads sew almost as well as the single colours. When stitching on white card the antique silver thread stands out much better than standard silver.
One multi stranded that I find very challenging is called lily pond. This has a strand of what looks to me to be a strand of glittery plastic. The results are very pretty. However, I would recommend working with short lengths of lily pond as it tends split apart after going through a number of holes.
You should find Kreinik thread in your local needlework store. If not then Kreinik have a store locator on their web site.