What kind of cards do you want to make? Exactly what kind of metallic cardstock is it? Foil? Shimmery? Other?
Can you use it as a background and add embellishments over the top of it instead of trying to print or write directly onto it?
Can you use letter stickers over it instead?
Here are a few examples of mine:
On this one, I couldn't write or print on the glitter cardstock, so I used layered items over the top of it.
Baby boy By Here Kitty
Instead of writing or printing on this embossed background, I just put the sentiment on another element and added it.
Embossed birthday wishes By Here Kitty