The term 'strong metallic element' can be summarized by the crossword solution of titanium, which is an 8-letter word. Titanium is a chemical element with the symbol Ti and atomic number 22. It is a lustrous transition metal with a silver color, low density, and high strength. It is highly resistant to corrosion in sea water, aqua regia, and chlorine. Titanium is used in aircraft, armor plating, naval ships, spacecraft, and missiles due to its light weight and strong nature.