When using lightning lure, the damage states that to take damage the target must be within 5ft of you. 
If the target ends up within 5ft of you after being pulled, does that trigger the damage.

Also, it says you can use your lightning lure to pull creatures up if you’re flying, but does that not apply to you pulling flying creatures down as well?

Let's look at the exact text of the spell:

The target must succeed on a Strength saving throw or be pulled up to 10 feet in a straight line toward you and then take 1d8 lightning damage if it is within 5 feet of you.

Yes, the spell pulls the target to within 5 feet of you and then damages them (unless it's unable to pull them that close due to things like stacking limits).  You can always pull an airborne creature toward the ground

I've had my Artificer character use lightning lure for the express purpose of pulling someone out of a pit of monsters, and they had to end up within 5ft of me to be out of the pit, so it did the damage.

(Later decided to change to thorn whip for smaller damage die and more range, even if it always causes the damage on a hit.)

It's also possible to pull them only partway to you, especially if there is a barrier or a person in the way.

Quote from naruhoodie >>

(Later decided to change to thorn whip for smaller damage die and more range, even if it always causes the damage on a hit.)

Yeah I've never seen the point of lightning lure personally; its range isn't great and the damage isn't that good. The main points in its favour are that its less commonly resisted and its a saving throw cantrip, so might have better odds against some enemies.

While thorn whip has a more commonly resisted damage type, it's magical (so counters some of that), has better range, and it's actually a ranged melee attack which creates a couple of interesting little bonus combos (e.g- you can deal the extra damage from absorb elements with it at a distance).

Rules-wise with lightning lure the assumption seems to be that because its range is only 15 feet it will almost always pull the target to within 5 feet of you, so almost always deals the damage. But it's a bit weird to construct it that way as all this does is make it mostly worthless to use with the Distant Spell Metamagic (or anything else that can increase your range) and creates annoyances if your target snags their pocket on a door handle or something so doesn't get pulled the full distance.

Only swarms have resistance to piercing damage, which would include magical. They also have resistance to bludgeoning and slashing.

All forced movement is powerful when battlefield control and melee characters are involved.

Quote from Haravikk >>

Quote from naruhoodie >>

(Later decided to change to thorn whip for smaller damage die and more range, even if it always causes the damage on a hit.)

Yeah I've never seen the point of lightning lure personally; its range isn't great and the damage isn't that good. The main points in its favour are that its less commonly resisted and its a saving throw cantrip, so might have better odds against some enemies.

Given that it debuted in Sword Coast Adventurer's Guide, I suspect that Lightning Lure was intended to help out the Storm Soul sorcerer pull targets close so they could use their  Heart of the Storm ability more easily.

Yeah. Not long after the lightning-lure a party member out of the pit, my character and nearby party members were surrounded by twig blights, so not able to use ranged attacks without disadvantage, and I wouldn't be able to lightning-lure anything else close enough to shock it.

Although maybe I could've used lightning-lure on one of the blights already right next to me? How would you rule that situation?

In any case, thorn whip would've been more helpful there, since as a non-ranged attack, I could use it on further-away creatures without disadvantage (though probably the blights would've provided +2 AC from partial cover.) And I wound up casting absorb elements so using the extra damage with the thorn whip would've been very nice.

Quote from naruhoodie >>

Yeah. Not long after the lightning-lure a party member out of the pit, my character and nearby party members were surrounded by twig blights, so not able to use ranged attacks without disadvantage, and I wouldn't be able to lightning-lure anything else close enough to shock it.

Although maybe I could've used lightning-lure on one of the blights already right next to me? How would you rule that situation?

If they fail their save, they get pulled 0 feet, then take damage.

Quote from 6thLyranGuard >>

Given that it debuted in Sword Coast Adventurer's Guide, I suspect that Lightning Lure was intended to help out the Storm Soul sorcerer pull targets close so they could use their  Heart of the Storm ability more easily.

That makes a lot of sense actually; to be clear, while I think lightning lure isn't an especially good cantrip in its current form, I do like that it exists, I like that there is another option for pulling a target, and with a different damage type.

But mechanically it desperately needs improving; I mean it's literally 50% of the lightning cantrips in the entire game, and the only ranged one (though not by much) and it's just… meh. The problem is especially obvious for Artificers who have both lightning lure and thorn whip on their spell list as standard (as opposed to those who only have lightning lure and need a feat or whatever to get thorn whip), as the moment you've got a choice lightning lure is pretty much always going to lose unless you've got a thematic reason to not take thorn whip.

Yeah, I've tried to think up builds where I'd actually want to take it and... I just can't.

Yeah, I had a thematic reason for having a lightning cantrip, and lightning lure seemed to have some of the benefits of both shocking grasp and thorn whip, but as it played out, switching to those other 2 cantrips would be more useful (for Absorb Elements reasons if nothing else.)

I know this is an old thread, but I wanted to share this.  I have an Eldritch Knight, he gets a bonus action melee attack when casting a cantrip.  So I would move within 15' of an enemy in melee combat with a member of my party, then cast Lightning Lure to pull the enemy towards me (out of melee with my party member) and melee attack him as a bonus action.  Now the enemy is in melee with me and not the vulnerable party member.

If an enemy is within 5ft of me , and i attack with lightning lure then is it a automatic hit or they still can make a saving throw and avoid damage .

Quote from Solu_Chan >>

If an enemy is within 5ft of me , and i attack with lightning lure then is it a automatic hit or they still can make a saving throw and avoid damage .

They still need to fail the saving throw, because the damage is part of the result of failing (enemy is pulled then takes damage if they're within 5 feet).