How can I bond a melamine piece to metal?

You can use Poxipol.

Before using it, make sure the surfaces to be joined are clean, dry, and free of grease or rust. Sanding very smooth or shiny surfaces is recommended.

It is very easy to use—follow these steps:

1) Dispense equal parts of each component. Make sure to apply a bead of at least 2 cm of each component.

2) Mix for at least approximately one minute, until you obtain a uniform color.

3) Apply the mixture to one of the surfaces to be joined and keep the parts held together for 10 minutes.

Keep in mind that the product hardens in just 10 minutes, but reaches its maximum strength after 24 hours.