How the metallic alloys change the molecular properties?

Also what is crystal formation from the metal and non-metal bonding?

Alloys are materials that contain more than one element and it has the characteristics properties of metals - they are ductile, malleable and good electrical conductor.

Alloys can be of a heterogeneous mixture. This means that its component materials are not uniformly distributed. No matter how structured the alloy is, when you combine a metal with another metal, it would change its properties. Taken for example, bronze which is the first substitutional alloy, which was used more than 3000 years BCE. Bronze is composed of 70 to 90 percent of copper that is mixed with tin. The resulting alloy has better qualities that are increased in durability, easier melting, and casting and it's much stronger, harder and more resistant to corrosion than pure metals.

Metallic bonding, however, is a type of chemical bonding that arises with electrostatic force between conduction electrons and a positively charged metal ions. To understand why alloys are much stronger than pure metals, it must be taken into consideration that metals are crystalline solids. When a metal is mixed with another metal to produce a substitutional alloy, the less abundant atoms of the solute element disrupts the crystal lattices of the more abundant element. This makes it harder for planes of the material to slide past each other, which makes the alloy hard and strong.