Magnesium alloys, whether cast or wrought (extruded), have very good strength to weight and low density. They weigh around 30% less than aluminium and 75% less than steel. This makes them very useful in weight critical applications, in particular aerospace and motorsport where speed or fuel efficiency are priorities. Depending on the grade, they have excellent casting and machining properties, and are suitable for the production of intricate profiles.

Cast alloys have considerably lower manufacturing costs than wrought types, because they are manufactured in a single step from molten alloy. Wall thickness can be as little as 0.5 mm with good mechanical properties. Wrought types, formed by extrusion, rolling and forging, have superior and more consistent mechanical properties, but their poor workability (low ductility) makes them harder to process into parts.

The ASTM code for alloying elements is as follows: aluminium (A), zinc (Z), manganese (M), silicon (S), yttrium (W), rare earth (E), zirconium (K), silver (Q) and thorium (H). The principal families are AZ (aluminium-zinc), AM (aluminium-manganese), AS (aluminium-silicon), WE (yttrium-rare earth) and AE (aluminium-rare earth). For instance, AZ91 Mg-Al alloy contains 9% aluminium and 1% zinc.

Magnesium alloys are not widely used outside of aerospace and motorsport, because they are relatively expensive, vulnerable to corrosion and wear, not very stiff and quite brittle. They are often surface coated, to prevent them reacting with the environment, and help avert galvanic corrosion with other conductive materials placed closely. There are many options available, such as painting and electroless nickel plating. Plasma electrolytic oxidation (PEO) is another option, which yields a highly durable ceramic coating on the surface. Anodising aluminium is a form of electrolytic oxidisation. The introduction of plasma results in a harder oxide film, inert surface and reduction in stiffness (reduces brittleness). It is suitable for aluminium and titanium, as well as magnesium.

Certain grades of magnesium are biocompatible and being explored as resorbable metal implants (biodegradable). It has potential to be used for healing bone, for example, in which case it is resorbed by the body over several months. The relatively low stiffness of magnesium (closer to the mechanical properties of bone than titanium, for example) and lack of toxicological tissue response mean it is potentially suitable for temporary orthopaedic implants.

Magnesium has a significant carbon footprint as a result of the manufacturing process. The most common method is the Pidgeon process, which involves several steps and requires a large amount of energy and consumables. Temperatures up to 1,200 degC must be maintained in order to extract the primary magnesium from its ore (calculated dolomite). There are alternatives to the Pidgeon process, which are less energy intensive, such as electrolysis (8.5 kgCO2e/kg versus 21.8 kgCO2e/kg for Pidgeon). However, it has not been adopted in China, where the majority of magnesium is produced.