Barium compounds are added to fireworks to impart their green color. Barium sulfate is used as an insoluble additive in oil well drilling fluids. In its purer form, it is used as an X-ray contrast agent for imaging the human gastrointestinal tract. Water-soluble barium compounds are toxic and have been used as rodenticides.

Barium is a soft, silvery-white metal that has a golden tinge when ultra-pure. [6]: 2 The silvery white color of barium metal disappears rapidly after oxidation in air, producing a dark gray layer containing oxides. Barium has medium specific gravity and high conductivity. Because barium is difficult to purify, many of its properties have not been accurately determined. [6]: 2

At normal temperature and pressure, metal barium has a body-centered cubic structure, the distance between barium and barium is 503 picometers, and the heating expansion rate is about 1.8×10−5/°C.

Barium is chemically similar to magnesium, calcium and strontium, but more reactive. It usually exists in the +2 oxidation state. Most exceptions are a few rare and unstable molecular species that are only characterized in the gas phase, such as BaF, [6]: 2 But in 2018, the presence of barium(I) species was reported in graphite intercalation compounds. [8] Reactions with chalcogens are highly exothermic (release of energy); reactions with oxygen or air occur at room temperature. For this reason, barium metal is usually stored under oil or in an inert atmosphere. [6]: 2 Reactions with other nonmetals such as carbon, nitrogen, phosphorus, silicon, and hydrogen are usually exothermic and proceed with heating. [6] ]: 2–3 The reaction with water and alcohol is exothermic and releases hydrogen:[6]: 3

Ba + 2 ROH → Ba(OR)2 + H2↑ (R is an alkyl group or a hydrogen atom)