Running along Melemele Island's north side, Route 3 is a sizable stretch that connects Route 2 in the northwest with Route 1 at its southeast end. Travelers must keep a sharp lookout for the shadows of overhead Pokémon that may swoop down and strike at any moment! Knowing that, you can still take in the tranquil beauty of Melemele Meadow as you explore this long, winding route.
Professor Kukui lost Lillie somewhere along Route 3, so you'd better make a thorough search of the area. You can avoid or choose to engage the battle-ready Trainers here, but again, be aware of the shadows of Pokémon that are circling overhead—for stepping into a shadow sends a wild Pokémon swooping down on you.
When the path splits at the sign, take a left. You get to battle a trainer here.
Melemele Meadow is a serene, secluded place filled with fragrant flowers—and plenty of wild Pokémon that frolic among the flora. Rare species can be caught here.
Apparently, Lillie wasn't on Route 3, but in Melemele Meadow. It seems that little Nebby has taken off on its own again, and Lillie needs your help to get it back. It enters a small hole and into a cave. Lillie restores your Pokémon, and you can speak with her again at any time to have them restored.
Follow the path downward to find a Great Ball. Head through the meadow's thick flower fields. As you do so, Rotom will give you a temporary EXP boost. If you see sparkles in the flowers, press A on them to collect Yellow Nectar. Go up the ramp and collect the Net Ball on the ledge.
Oricorio is one of the many colorful Pokémon found in the Alola region. It changes its appearance—and even its type—based on the nectar of the flowers upon which it feeds. Keep your eyes peeled for more Oricorio, as different Oricorio will appear around different-colored flowers. And pick up any Yellow Nectar you find in Melemele Meadow.
Go around to the right and hop off the ledge at the top. There is a hidden Honey in the nearby boulder. Head through the flowers and up the ramp. Go around left to find some Yellow Nectar. Down from there is a Poison Barb. Climb up the hill and you'll find an aspiring Actor who introduces herself as Meredith. Apparently, she's trying to learn different acting styles from Oricorio and will ask you to help her out by battling her.
After the battle, she heads off to a new location. Head back to where Lillie is, and go downward through the flowers. You'll see a small hole in the meadow's west, which lets adventuresome travelers slip into the dark confines of Seaward Cave.
They leave after a short conversation. Go further down and you'll find a Heal Ball. Head down some one-way ledges. Jump down each one, and on the way, go north to find an Expert Belt. Go right from there and head down some ledges. You'll eventually find the exit, but before going out there, go down and follow the path, and go down when the path splits and check on the rock to find a Star Piece. Then go back up and go left to find a Super Potion. The rock above that has a hidden Stardust. Then go up and right from there to get a Never-Melt Ice, which raises the power of Ice-type moves.
Now go back the way you came and go downward when the path splits. Then go toward the right to reach the cave exit.
Go up to get a Dive Ball. If it's night, you can talk to the Swimmer and say "Yes" to see sparkles in the water from Finneon.
To the left of where you exited the cave to find some sparkles. You'll find a bottle with a faded letter. When you go back to Iki Town, you can deliver this letter to the writer's little sister. When you find her back in Iki Town, she will give you some Stardust as thanks.
Seaward Cave[]
Go back into the cave, and head back and talk to Nebby, who'll take you back to Lillie.
Melemele Meadow[]
Lillie will thank you and restore your Pokémon before you head back out to Route 3, where Hau is waiting.
Route 3[]
Hau has just completed Ilima's trial, and he's feeling like he could take on the world. He's ready to battle you right away.
Hau has certainly been hard at work training his Pokémon. Their levels have increased significantly since your last battle, and his Pichu has evolved into Pikachu. Its Static ability may leave your Pokémon with paralysis, so be ready with Paralyze Heals or other medicines that can cure these status ailments. He also added a Noibat to his team.
Professor Kukui appears after you wrap up your battle with Hau. He's happy to see that you've found Lillie and informs you that your next test will be to battle none other than KahunaHala himself, in what is known as the grand trial. Explore the rest of Route 3 on your way back to Iki Town, where Hala awaits.
Go in the same direction Hau and Kukui went. Here you'll find a bridge. Talk to the man nearby and he'll give you a Soothe Bell. Go across the bridge where you can battle another trainer.
Go a little farther down the path and you'll find a Super Potion. Go back up across the bridge and talk to the guy on the left. He won't battle you until you have defeated every trainer on the route, which you now have done.
The Sightseer hanging out just past the bridge asks you to catch him a Sableye at Ten Carat Hill. He'll give you 3,000 for it, but you don't have access there just yet.
When you're ready to tackle your grand trial, follow Rotom's guidance to find your way back to Iki Town.
Heal Ball, then continue onward. You'll have to face another trainer.
Sharp Beak. Follow the red flag on the map to Melemele Meadow.
Great Ball. Head through the meadow's thick flower fields. As you do so, Rotom will give you a temporary EXP boost. If you see sparkles in the flowers, press A on them to collect 
Yellow Nectar. Go up the ramp and collect the 
Net Ball on the ledge.
Honey in the nearby boulder. Head through the flowers and up the ramp. Go around left to find some 
Poison Barb. Climb up the hill and you'll find an aspiring Actor who introduces herself as Meredith. Apparently, she's trying to learn different acting styles from Oricorio and will ask you to help her out by battling her.
Escape Rope. Go further down and you'll find Nebby. Suddenly you are approached by the Ultra Recon Squad. DulseUS/SolieraUM approaches you to battle you.
Expert Belt. Go right from there and head down some ledges. You'll eventually find the exit, but before going out there, go down and follow the path, and go down when the path splits and check on the rock to find a 
Star Piece. Then go back up and go left to find a 
Super Potion. The rock above that has a hidden 
Stardust. Then go up and right from there to get a 
Never-Melt Ice, which raises the power of Ice-type moves.
Dive Ball. If it's night, you can talk to the Swimmer and say "Yes" to see sparkles in the water from Finneon.
Paralyze Heals or other medicines that can cure these status ailments. He also added a Noibat to his team.
Soothe Bell. Go across the bridge where you can battle another trainer.
TM59 (Roost).
3,000 for it, but you don't have access there just yet.