If a Pokémon (let's say Alcremie) uses Metronome and gets Multi-Attack, will it become that Pokémon's type or stay Normal?
The type of Multi-Attack depends on the type of memory held by the user, being Normal-type if there is no held memory.
So I think if Alcremie is holding, say, the Fighting Memory, it will turn into a Fighting type move.
Source
Hope I helped!