In screen printing, there are at least two methods for obtaining a metallic effect on your print.
You can use, for example, glitter and powder: simply add them to a transparent base (and a binding agent for metals, if using Modatex ink).
We recommend using this method with low thread counts.
Another method involves putting a layer of water-based or Plastisol-based screen glue onto the item to be screen printed on, leaving it to dry and then placing a thin sheet of foil on top of it.