Gallium attacks most other metals by diffusing into their metal lattice. Gallium, for example, diffuses into the grain boundaries of Al/Zn alloys or steel, making them very brittle. Also, gallium metal easily alloys with many metals, and was used in small quantities as a plutonium-gallium alloy in the plutonium cores of the first and third nuclear bombs, to help stabilize the plutonium crystal structure.
