Magnesium
Magnesium is 1/3 density of Aluminum and between 10 to 15% density of Iron.
It can be ignited in water although it has low ignition point.
It helps prevent corrosion in Aluminum.
It makes the metal dull.
Amongst shines Aluminum in metals is closest to mirror finish reflective.
It is found in ores and also in sea water.
It is used as antacid in pharmacy.
Without Magnesium the plants will cease to be green, because it helps the photosynthesis process and we all will die of starvation.

Which Metal is in Liquid State on Room Temperature?
(1) Chromium,  (2) Magnesium,  (3) Manganese,  (4) Mercury