The "most metallic" element can be interpreted in a few ways, so the answer depends on what criteria you're using:

* By electronegativity: The element with the lowest electronegativity is francium, with a value of 0.7. This means it's the least likely to gain electrons and therefore acts most metallic.

* By metallic character: Cesium is generally considered the most metallic element due to its high reactivity, low ionization energy, and tendency to form cations.

* By density: Osmium is the densest element, with a density of 22.61 g/cm³. While density isn't directly related to "metallic" character, it often correlates with the presence of tightly packed metal atoms.

So, depending on your definition of "most metallic," the answer could be francium, cesium, or osmium.