Sheet aluminum comes in a variety of colors , as well as mill, bright and brushed finishes at .040 gauge, and fewer colors in thicker gauges. It is relatively lightweight and flexible at .040. It can be bent to create a box shape, as well. It is waterproof, and will last up to about 15 years outdoors.
Polypropylene Plastic Sheets come in a variety of colors and are an inexpensive short-term material. It is lightweight, fairly rigid, waterproof and will last up to about 5 years outdoors. It comes in 4mm, and a 10mm in white only.
Aluminum Composite panels are like a sandwich of the two above materials. At 6mm thick, it has more rigidity than sheet aluminum, but is still fairly lightweight. It comes in a variety of colors at 6mm, and white only at 10mm. It is waterproof, and will last up to about 15 years outdoors.
Also known as Sintra and Celltec, comes in a variety of colors at 3mm and 6mm and white in thickness up to 1”. It is a bit heavier, and can be routed for shapes and letters, and custom painted. It is waterproof, and will last up to about 10 years outdoors.