Time Stop is a glitch done by interrupting certain actions such as using a bottled content or dying. It causes the camera to get stuck next to Link and time doesn't move during it. Time Stop is useful, because during it, cutscene triggers cannot activate, allowing Link to walk past them and it can also be used for Song Storage detailed below.
Song Storage is done by performing Time Stop in front of a Gossip Stone. Doing so causes the Ocarina menu to pop up, which gives you the ability to play songs while moving. Playing a song like Song of Double Time and going through a loading zone will store it. You can activate the stored song just by opening the inventory and moving the cursor on any item with text to get the song text out after exiting the menu. A stored song can be stored again just by going through a loading zone again.
If there's a gossip stone near any kind of ledge, by slashing your sword and hitting the Ocarina a moment after the slash, Link will fall and the ocarina staff will appear in the bottom screen. This way you can store songs like the TimeStop method, by going in loading zones. (Video below in the "Death Method" section.)
When you have a Bottle on B, Link will not put it away when you target and shield making Time Stop way easier to do and like in the original MM.
For some reason when you're underwater with Zora Link and you have a normal bottle on hand, when you target and shield, Link will not put away the Bottle making it so you can do Time Stop underwater just like the Bottle on B Method.
By dying in air and grab a heart before touching the ground, will revive Link and puts him in TimeStop mode. This "easy-normal" method was fixed in MM3D. If you store the Song of Time and die in the air and hit A before touching the ground, the game will automatically give you 3 full hearts not letting Link die and stay in TimeStop mode because you never picked up a heart or fairy during the process.