3DPrinting

Well, you can also download models from a number of websites rather than creating them yourself (Thingiverse is probably the largest and most mature site; there's also Printables, Cults3D, MyMiniFactory, and a few others). A slicer is kind of required, yes; my printer shipped with get-started software that included a slicer, but it isn't a Bambu and I have no idea what that company might provide.

As for the plastic/metal filaments, It's Complicated. I've seen one variety that invites you to send the printed pieces back to the filament's manufacturer, who will then anneal it for you in an industrial furnace that can probably get hot enough to melt bronze, copper, or iron (~1200C for iron, ~1000C for the other two—very few metals need a full 2000C!). Tin should melt, or at least soften, in an ordinary stove (<250C melting point), so you could successfully melt a tin-filled filament at home. And melting most of the plastic out while leaving behind just enough to act as glue can be done in theory. However, many metal-filled filaments are not intended to be annealed ( Here's a product page for FormFutura copper-filled filament—you'll note that the post-processing suggestions do not include melting out the plastic). These types are more "for the looks".

If you're looking to print physically strong parts, you may be better off working with PC or nylon than trying to get metal out of an additive printer. Full-strength metal parts are best produced by a subtractive process, for example on a CNC machine.