Bismuth (element)
鉍 is a rare kanji that refers specifically to the chemical element bismuth. It has no broader conceptual center beyond this single, technical meaning.
鉍 is a modern coined character for the element bismuth, combining the metal radical 金 with the phonetic component 必 (ヒツ). It was likely created in the 19th or 20th century as part of systematic chemical nomenclature.
The left side 金 (metal) tells you it's a metallic element. The right side 必 (certainly) can remind you that bismuth is certainly a metal. Together, 鉍 is the metal bismuth.
For ヒ, imagine a heater made of bismuth: the 'he' in heater sounds like ヒ, and the metal 金 conducts the heat.