Why can a hydrogen atom form a covalent bond without fulfilling the octet rule?

hydrogen’s valence shell can hold only up to two electrons.
hydrogen’s valence shell never needs to be full to be stable.
the octet rule only applies to bonds formed by trading electrons.
the octet rule only applies to alkali metals and alkaline earth metals.

Answer;

Hydrogen's valence shell can hold only up to two electrons.

Explanation;Covalent bonds are types of bonds that are formed between non-metals as a result of sharing electrons between atoms. Atoms will covalently bond with other atoms in order to gain more stability, which is gained by forming a full electron shell. By sharing their outer most electrons, atoms can fill up their outer electron shell and gain stability. According to octet rule, When atoms react, they tend to achieve an outer shell having eight electrons. This is not the case for hydrogen as it obtains a stable valence shell configuration by sharing a single pair of electrons with another atom.