Corten steel is very popular these days, so why not planters made of this material -- from Nice Planter. These planters are made from folded metal, so there's no welding, and the five panels interlock together. Corten is usually found in modern gardens, and this trough planter would fit perfectly. It comes in two sizes, 16x46x16 or 20x46x16.
Also comes in a 16" or 20" square.
These planters arrive in a bare steel state and weather to the golden brown rust color. Manufacturer recommends placing them on grass during weathering to avoid staining adjacent materials.
The aluminum and stainless planters come in the square and trough shapes.
Great choice, as they are large enough to accommodate large-ish plants and of course are perfect outside.
See them all at www.niceplanter.com