Many of these compounds are pyrophoric (flammable by spontaneous chemical reaction in air). They produce highly flammable gases in the presence of acid. The metal hydrides are combustible. Combustion of all compounds in this class produces irritating and toxic gases.

Materials in this group are reducing agents and react rapidly and dangerously with oxygen and with other oxidizing agents, even weak ones. Thus, they are likely to ignite on contact with water, alcohols, and acids, forming flammable hydrogen or hydrocarbon gases which ignite due to the exothermic nature of the reaction. Hydrides are incompatible with acids, alcohols, amines, and aldehydes.

Extremely corrosive and irritating to mucous membranes, eyes, and the respiratory tract. Fumes are a serious inhalation hazard. Some of these materials are gases and are extremely poisonous by inhalation.

Compounds in this group are generally used as reducing agents in industrial chemical synthesis and may act as catalysts. Metal hydrides and silanes are used as sources of the hydride ion (H-). This group also includes organomagnesium (Grignard) reagents and organolithium reagents, which are strong carbon bases and are used as alkylating agents in organic synthesis.

The metal compounds covered in this group contain main group metals (Groups 1A, 2A, and 3A) which form non-redox-active cations. The hydride, alkyl, and aryl compounds of transition metals are generally less reactive than those of the main group metals, and they are covered in Group 42, Organometallics.

Aluminum borohydride, aluminum hydride, calcium hydride, diborane, lithium aluminum hydride, lithium hydride, magnesium hydride, sodium borohydride, sodium hydride, trimethylsilane, butyllithium, methylmagnesium bromide, phenyllithium.