Metcalf will also be fined $555,556 in total across both games. He'll be eligible to return to the team's active roster on January 5th.
Metcalf was at the center of controversy on Sunday after clashing with a spectator during the second quarter of the Steelers' 29-24 defeat of the Lions at Ford Field.
The incident escalated when Metcalf grabbed the fan's blue wig, and he appeared to aim at a blow at the spectator before walking away.
It was not clear what had led to the incident, although US media reported on Monday that Metcalf had reported the same spectator to security during a previous visit to Ford Field.
The NFL said Metcalf had broken league rules concerning interaction with fans.
"Metcalf's actions violate league policy, which specifies that players may not enter the stands or otherwise confront fans at any time on game day and ... if a player makes unnecessary physical contact with a fan in any way that constitutes unsportsmanlike conduct or presents crowd-control issues and/or risk of injury, he will be held accountable," the league said.
US media reports said Metcalf plans to appeal the suspension. If his ban is upheld, he will miss the Steelers' final two games of the regular season against the Cleveland Browns and Baltimore Ravens.