Materials used in outdoor furniture
Steel/Wrought iron: very traditional, usually painted for exterior use and often quite ornamental in appearance (pierced, scrolled, etc). Generally these heavier metals are used to create larger furniture sets, such as a table and four chairs, which will not often be moved around. Some care must be taken with their maintenance to avoid rust.
Aluminum outdoor furniture may be either cast or extruded. Cast aluminum is (and looks) heavier and stronger. The great advantage of aluminum is that it is both weatherproof and tough, without being as weighty as steel. It is ideal for modern or bistro-style furniture. It also forms the inner frames for pieces of synthetic rattan wicker furniture.
Cane or rattan is another traditional material for furniture in conservatories or sun-rooms, usually woven in strips over a frame of rattan poles. Rattan outdoor furniture will need to be kept in a semi sheltered area unless it has been treated for rain resistance, however it does resist heat well. However, synthetic wickers and rattan look-alikes of all kinds woven onto aluminium will provide you with more or less realistic versions of the ‘real thing’ which have the advantage of being waterproof.
Resin/plastics: now available in all kinds of finishes imitating everything from marble to birds-eye maple. Plastics are lightweight and waterproof and can be woven into synthetic wicker over a frame for a weatherproof rattan look. Check the specifications as different kinds of synthetic materials can behave very differently in sunlight, frost etc.
Glass: easy to clean, light and bright and usually available as the tempered ‘safe-break’ variety in case of accidents. It can be heavy to move around and of course is best suited to a modern décor. Glass may be used as a table-top alone in combination with a steel or wooden frame, or you may find a whole table made of folded glass.
Wood: hardwoods are longer-lasting and have a closer grain, while softwoods are not so strong. Wooden furniture needs pre-treatment for use outdoors, especially to withstand damp or hot conditions, and must be carefully maintained. Wood warps, splits and decays in extreme conditions so it is best to bring wooden furniture indoors in hard winters (or summers). Having said all that, it is a beautiful material which often complements a garden space very sympathetically and is comfortable to sit on and eat from.
You can also learn more about garden lighting and other outdoor tips on my friends site.