The Best Glue Ever is the perfect adhesive for your metal embellishments. And it doesn't take a lot of glue, either.
For my project, I had a piece of die cut grungeboard and some metal pen nibs. I placed small dots of glue along the grungeboard as well as the nibs - you can see just how little you need. Then I just let the glue dry.
Once the glue was dry and tacky I just placed my pieces on my project - in this case a tag. Perfect!