Applying Protective Coating
Metal and wicker furniture can generally stay outdoors due to their resiliency to the elements. Aluminum furniture, in particular, has powder coating to eliminate any chances of rusting due to condensation. Nevertheless, applying some car wax to metal adds an extra layer of protection if you expect winter conditions to be harsh.
Wicker also stays in good shape when left outdoors. But Bob Vila above warns about natural rattan needing a dark and dry place for storage due to the potential of drying out.
Check out the full article to get all the outdoor furniture tips.