Sheet metal bend features are often used to join sheet metal faces that were created in a particular location to meet specific design criteria. By selecting edges on existing sheet metal features, material is added to the model using the bend radius and material thickness defined by the sheet metal style.
Faces extend in compliance with your default (or selected) bend radius. If the faces are parallel, but not coplanar, you can add a double bend. Depending on the distance between the faces, the bends are either trimmed so they are tangent or a new face is created between the two bends.
You can also override default sheet metal styles from the Bend dialog box as you create your sheet metal bend. These settings include how the flat pattern unfolds, and the bend relief settings between faces.