Plastic furniture is all right indoors, especially if it is in the high-styled modern idiom, and was created by or emulates that of 1950s and 1960s designers such as Eero Saarinen. But outdoors, one ideally will have garden or patio furniture made from wrought iron or of teak-wood, which will not deteriorate from exposure to the elements. Wooden and iron furniture exists in perfect harmony with landscaping and nature, especially when made in greens, browns, and other earth-tones.
Here is my old garden courtyard, where I had outdoor dining furniture by the now-defunct, elegant wrought-iron furniture company Lyon-Shaw
, and a smaller chat-table in iron, wicker and tile, by Alfresco Home