In Main Phase 1 (メインフェイズ１, Meinfeizu Ichi), the Turn Player may:
- Normal Summon, Tribute Summon, or Set a monster.
- Special Summon a monster(s).
- Manually change the Battle Position or perform a Flip Summon on a Monster Card, provided it was not Set or Summoned this turn.
- Activate effects, such as those of "Barrel Dragon" or "Blowback Dragon".
- Activate or Set Spell and/or Trap Cards of any speed. Quick-Play Spell Cards and Trap Cards cannot be activated in the turn they are Set.
If a particular monster wasn't Summoned this turn, the Turn Player can flip it face-down using its effect (such as with "Guardian Sphinx" or "Swarm of Scarabs"), and then perform a manual Flip Summon on it, since the rules state that only one manual Battle Position change may be performed per turn; Battle Position changes by effects do not count towards this.