Why is Hydrogen, H, most often considered a nonmetallic element?

Because at room temperature it is a gas, maybe?

Because it totally lacks metal properties. See:
http://en.wikipedia.org/wiki/Metal

The hydrogen doesn't have any metallic elements.

Hydrogen is most often considered a nonmetallic element for several reasons. First, it is a gas at room temperature, which is a characteristic commonly associated with nonmetals. Many nonmetallic elements, such as oxygen and nitrogen, are also gases at room temperature.

Secondly, hydrogen lacks the typical properties of metals. Metals generally have high electrical and thermal conductivity, malleability, and a shiny or metallic appearance. Hydrogen does not possess these properties and, therefore, does not exhibit typical metallic behavior.

To determine whether an element is metallic or nonmetallic, we can refer to the periodic table. Hydrogen is located in Group 1, which consists of the alkali metals. However, even though it is in the same group as metals, hydrogen is generally considered a nonmetal due to its atomic structure and properties.

It's important to note that the classification of an element as metallic or nonmetallic is not always black and white, and some elements may display properties of both categories. However, based on its characteristics and behavior, hydrogen is most often classified as a nonmetal.