If I want to print metallic colors (gold copper silver with a laminated effect) which shade should I use on screen? Will it be better in RGB or Pantone?
True metallic colours are printed using metallic inks which are spot colours, often a Pantone Metallic ink - i.e. an ink which contains metallic particles and other pigments. In lithographic printing, a spot colour requires its own separation and printing plate. It can't really be simulated in CMYK litho or digital printing, or in inkjet printing.
Also in letterpress printing, hot foil printing is sometimes used for metallic effects - basically, a cast metal die is used to stamp out a design from a sheet of foil onto the paper. This has a much shinier/reflective finish than a metallic lithographic ink.
If you don't want to employ these special printing techniques, then it is possible to simulate the look of metal by creating a design which looks like reflective metal, but it would have to be drawn/painted to look like that, and it won't be reflective like real metallics. Then you can just print it with a regular inkjet printer, or in commercial full colour digital/lithographic printing.
Here's an example of a design which looks like metallic gold, but isn't really. It's just made of several vector shapes with gradients and fills.
As for which colours to use, find some photos of real gold, copper, or silver objects, and sample the highlights, shadows, and midtones. Three or more colours should be enough to create the illusion of reflective metal.
I guess you want to know what color type should be used in a version which will be watched on normal computer screen.
You can well use RGB instead of metallic paint because computer screens do not show anything else. (except as converted to RGB)
If your metallic prints are shiny, it can be simulated in RGB, but not in spot colors (except if you have tens of them). See the following examples:
The first is a mild version, the object has a three stop gradient fill. The second version is strong. It has single solid color fill, but Photoshop's layer style Bevel&Emboss is added. It can create a wide variety of metallic effects.
These all are widely presented in tutorials. Search for "gold in Photoshop" and "gold text in Photoshop"
One degree more plausibility is available by using your shapes as masks for high quality photos of a real metallic surface. One photo can be enough, you only change the place where the clip is taken from and adjust the color to resemble the right metal.