The bronze copper is large — for a copper. From above, males and females look quite different. Adult males, when fresh and young, shine with purplish-bronze iridescence on the upper side; later, they are mainly just brown with some undistinguished darker spots. The female upperside forewings are orange, with a brown outer margin and several dark spots. The hindwing upperside, in both sexes, is brown with a wide orange outer band. Viewed from below, there is no apparent difference in the sexes; both have a whitish hindwing and coppery orange forewing, both with scattered black spots. The hindwing outer margin has a wide orange band.
Caterpillars are short and sluglike, with a covering of soft, downy hairs; color is yellowish green with a darker green stripe down the back.
- The gray copper (L. dione) is grayish white, not orange, on the underside forewing, and adults of that species fly only into July, not later.
- The American copper (L. phlaeas) resembles the female bronze copper from above, but viewed from below, its hindwing underside orange band is much thinner than the bronze copper’s wide one. Also, the American copper is much smaller than the bronze, having a wingspan of only ¾–1 inch.