This species, having a wingspan of 7–9 mm, has a bronzy appearance with metallic markings. The pre apical spot is broadly triangular (while more linear in A. treitschkiella).

The caterpillar is greenish-white. The head, prothoracic and anal plates are brown.

The mine initially starts as a short gallery, close to the leaf margin, that suddenly widens into a large blotch. That blotch often overruns the corridor.
See also bladmineerders.be

In preparation of ovipositing, which takes place at the bottom of the leaf close to the leaf edge, the female makes a number of 'trial punctures', which are later on, often still visible as a curving row of 2–7 brown spots perpendicular to the initial corridor. These trial punctures are typical for this species. If these punctures are absent, one must look at the Cornus-species: on Cornus mas it is A. treitschkiella and on Cornus sanguinea it is A. petryi.
The young larva initially constructs a short gallery in a leaf, close to the margin. Afterwards, this narrow mine suddenly widens into a large blotch that often overruns the corridor. Eventually, the larva cuts an oval excision of 6–7 mm long and crawls or falls with it to the soil. In this excision, from then on serving as a case, the caterpillar lives on, strolling around freely. Before winter starts, pupation takes place inside this case.
The adults are day-active in full sun.

A. metallella is monophagous on Cornus-species and the main hostplant is Cornus sanguinea and, more rarely, also C. mas.
C. alba and C. sericea are mentioned in the literature as well.