Metros were delayed by at least ten minutes, and metro traffic was partially at a standstill.

The metro service will run irregularly on Saturday afternoon, the Helsinki Regional Transport Authority (HSL) notes.
Earlier on Saturday, the metro did not run on the section between Kulosaari and Siilitie due to a power failure caused by a lightning strike.
The lightning struck near Herttoniemi metro station, disrupting metro services in Helsinki around 10:30 on Saturday morning. More specifically, according to HSL’s traffic emergency service, the lightning struck the metro tracks between Kulosaari and Siilitie stations.
People walking past the Herttoniemi metro station described the sound as “like a bomb had exploded.”
The explosive sound was even heard in the center parts of Helsinki.