What happens if all metals are melted together?

If you try to alloy all metals together, you get a complex alloy with unpredictable properties. Metals have different melting points, chemical reactivities, and structural features, so when mixed they can form various phases, intermetallic compounds, or even not fully mix, forming layers or inclusions.

In reality, such alloys are rarely used practically due to instability and deterioration of mechanical properties. Usually, a limited set of metals with compatible properties is chosen for alloy creation.

Example: bronze — an alloy of copper and tin, not all metals at once.