Furniture manufacturers typically employ the following methods to make aluminium or steel furniture:

Forging: This involves heating the metal to a required temperature. Thereafter, the workers will hammer the metal into the appropriate shape. In many cases, manufacturers use this method for producing wrought iron furniture. This requires the welding or bolting or various pipes and metallic pieces to arrive at the resultant piece of furniture.
Casting: This entails the use of a cast that bears the shape of the finished product. Workers pour the molten metal into the cast. Once the metal has solidified, they remove it from the cast.
Extrusion: This involves forcing molten metal through long pipes. It results in the formation of long, narrow tubes of metal, which will typically be hollow.

In terms of strength and durability, steel furniture remains unbeatable. This is true for both indoor and outdoor furniture items. Thus, when you purchase steel furniture, you can rest assured that it will offer you the best value for your money.