Lanthanum is a silvery-white, ductile metal that is highly reactive and can corrode quickly when exposed to air. It is found in minerals like monazite and bastnasite and is obtained through a process called ion exchange chromatography. It is used in various applications such as catalysts, optical lenses, and as an alloying element for other metals. Due to its scarcity and high demand, lanthanum and other rare-earth metals have become increasingly important in modern technology and are considered critical metals for many industrial processes.