1. A metal: When hydrogen loses its only electron, it becomes a positively charged ion (H+), forming a cation. This behavior is characteristic of metals, and it's why hydrogen is placed in Group 1 of the periodic table, along with alkali metals.

2. A nonmetal: When hydrogen gains an electron, it becomes a negatively charged ion (H-), forming an anion. This behavior is characteristic of nonmetals, and it's why hydrogen can also be placed in Group 17 of the periodic table, alongside halogens.

Therefore, hydrogen can exhibit both metallic and nonmetallic properties, making it a unique element.