Can you create stronger metals than what currently exists in metal by combining the right substances?

Answer

You can make alloys and thereby change the properties, including the mechanical properties.

Steel is an example of an alloy. In addition to iron (Fe), steel also contains carbon (C) and, depending on the steel type, other elements such as nickel (Ni), chromium (Cr), manganese (Mn), …

However, the mechanical properties are also very strongly influenced by the heat treatment given to the alloy. This allows one to change the arrangement of the atoms in the crystal lattice. Example: martensitic steel, which is very hard.