The bond that holds two hydrogen atoms together in a gas is a covalent bond.

Here's why:

* Covalent bonds form when two atoms share electrons. This sharing allows both atoms to achieve a stable electron configuration, similar to that of a noble gas.

* Hydrogen atoms each have one electron in their outermost shell. By sharing these electrons, they both achieve a stable configuration of two electrons, similar to the noble gas Helium.

* Diatomic hydrogen (H2) is the most common form of hydrogen gas, with two hydrogen atoms covalently bonded together.

Let me know if you'd like to know more about covalent bonds!