How do you transmute metal to become weapon?

You may find Beryllium Plutonium Uranium / Depleted Uranium Gold Gallium Steel Aluminum Copper among others. Older weapons may have had polonium in them too for old urchin-like initiation systems....

Get a PhD Physics degree, study nuclear engineering while doing that. Apply for jobs at the weapons labs (Los Alamos, Livermore, Sandia), if they accept you they will apply for a clearance for you,...

The axe became a weapon in prehistoric (neolithic) times. (Things usually become weapons as soon as they are developed).

they either give away electrons to metals to form a stable ionic compound or share electrons with other non metals to form a covalent compound

Metals are tarnished by the tarts at oxford uni