Step 1: Know what a transmission wire needs.
Power lines must carry current over long distances with as little energy loss as possible, and loss is governed by \[ P_{loss} = I^2 R \] so the metal chosen must have very low resistivity and must also be workable into long flexible wires.
Step 2: Check copper and aluminium.
Both have very low resistivity and can be drawn into long strands, aluminium being lighter and cheaper is what most overhead lines actually use, with copper used where cost is less of a concern.
Step 3: Check tungsten.
Tungsten has a much higher resistivity than either of these metals and is brittle, snapping rather than bending, which makes it completely impractical for stringing across pylons, it is reserved instead for bulb filaments where its high melting point matters more than low resistance.
\[ \boxed{\text{Tungsten}} \]