There are many steps in the transition that are not ironed out yet. However, there are some information available that are certainly accurate for the upcoming phases of ETH 2.0.
You can transition to the Beacon Chain which is Phase 0 (see this answer for all milestones). In that step there will be a deposit contract deployed on the legacy ETH 1.x ...
Metropolis is not a fork but a milestone in the Ethereum roadmap. Simplified:
Proof of Concept 1-8 (ETH 0.1) were several implementations of the Ethereum protocol in 2014 and 2015.
Olympic (ETH 0.9) was the last proof-of-concept testnet for Ethereum prior to the mainnet launch (2015).
Frontier (ETH 1.0) was the beta phase and the launch of the Ethereum ...