If your patio gets full afternoon sun, you're right to wonder if your furniture will become too hot to use. The short answer is yes, many common materials can become uncomfortably or even dangerously hot. However, the extent of the heat depends almost entirely on the material.
Dark-colored metals and certain plastics are the biggest offenders, absorbing intense heat and becoming scorching to the touch. Wicker and wood can also get very warm, though they may cool down faster. To avoid burned skin and enjoy your outdoor space, your best bets are light-colored aluminum, which reflects heat, or all-weather wicker designed for sun exposure. Dense woods like teak manage heat relatively well but still get warm.
For any furniture, adding thick, light-colored cushions can create a protective barrier. The most effective strategy, however, is to incorporate shade. A large umbrella, a pergola, or a retractable awning can dramatically reduce the direct sunlight that causes the heating problem. With the right material choices and a little shade, you can create a comfortable oasis even on the sunniest of patios.