Questions & Answers about Ich klebe das Bild an die Wand.
Both an and auf can translate as on in English, but they describe different kinds of contact:
- an = on / against a vertical surface
- an die Wand → onto the wall, against the wall
- auf = on top of a horizontal surface
- auf den Tisch → onto the table, on the table’s surface
A picture is normally attached to the vertical surface of a wall, so German uses an die Wand, not auf die Wand.
Auf die Wand kleben would sound odd and is usually only used in special contexts, like gluing something flat onto a wall as if it were a horizontal surface (e.g. when talking about paint or wallpaper in a very physical, surface‑oriented way), but even then an die Wand is far more common.