Why is the Earth core made out of metal?

Answer 1

Earth was largely molten when it was newly formed. The iron and nickel that now make up the core were the densest common materials, so they sank tot he center to form the core.

Answer 2

The Earth's core is made mostly of iron and nickel because these elements were present in the materials that formed the Earth, and they sank to the center due to the planet's early molten state and gravitational forces. This concentration of heavy metals create the dense and metallic core at the center of the Earth.