To work like a charm is to succeed perfectly and immediately. It worked like a charm.
The immediacy is the point, since something that eventually works does not qualify. A charm here is a spell rather than an ornament, which is where the magic comes in.
1phrasework like a charmTo succeed perfectly and immediately.
“A drop of oil made the hinge work like a charm.”
work like a charm is a phrase.
Practised in Idioms