Non-iron button-down shirts never need to be worried about. The button-down collar lends a laidback slant that works from business to pub; and the non-iron finish keeps you crease-free all day.
Heavier weight fabrics are warmer and firmer, and often make more business shirts than lighter ones.
Midweight fabrics split the difference: not too thick, not too breezy. Easy to wear in any season.
Cooler, lightweight fabrics such as linen make shirts perfect for warm weather, and for layering all year round.