Quote from icarob666 >>

I know it's a supposition, but if you are attacked twice from 2 different types of damage and use this to protect you, what will be the outcome type of damage of the melee attack

 This spell uses your reaction to cast, so unless you somehow get more than one reaction (which is possible if you multiclass as a Cobalt Soul monk), you can only cast it once per round. In the case of multiple reactions, I would apply the rule about combining magical effects (Chapter 10 in PHB and Basic Rules), which says that the effects of the same spell cast twice on the same target don't stack. So the second casting would remove the effects of the first.

If you suffer multiple elemental damage types at exactly the same time, I would say you have to choose which one the spell will work on.

When you take a reaction, you can't take another one until the start of your next turn. This means that you can't cast absorb elements in response to two separate damage types before the start of your next turn. Say you take fire damage from a fire elemental and then cold damage from a frost salamander. After being hit by the fire elemental you could cast absorb elements, granting you resistance to fire damage until the start of your next turn. However, if the frost salamander then hits you with cold damage before the start of your next turn, you can't cast the spell in response to that, as you've already used your reaction. Then your next melee attack will do an extra 1d6 fire damage, unless the spell was cast at a higher level.

Quote from glug0001 >>

I coupled this with green flame blade, hex and a flametongue longsword for my lv11 definately not melee based caster.

Bard 10

Hexblade warlock 1

1D10+Cha+Prof Slashing, 2D8+2D6 fire, +1D6 necrotic, +5D6 elemental damage (on 5th spell slot). Plus 2D8+Cha fire on a target within 5ft.

All using my charisma :)

This looks nice on paper, but you can only cast Hexblade's Curse on 1 creature per rest and it takes 3 bonus actions to activate Flame Tongue, cast Hex and apply Hexblade's Curse. By the third turn your target will probably be dead.

Also, other spells compete for your 5th and 6th level bard slots like Animate Objects with it's 10d4+40 bludgeoning damage per bonus action and Swift Quiver with it's 2 extra attacks per bonus action which can be taken as a Magical Secrets spell. Both last for 1 min.

Anyone know if a "melee spell attack" counts as a "melee attack" for purposes of this spell? Thorn Whip, for example, is a cantrip that's described as a melee spell attack.

It does.

Take notice that the spell has a somatic component.

So sword and shield fighters need either the warcaster trait, or risk it and drop their weapon during the reaction.

Dropping handheld items is free.

Ya, what egwythe37 said.   How much is the damage lessened?  There is no information about this in the spell description. 

Reread in the spell description. "You have resistance to the triggering damage type until the start of your next turn." Resistance halves your damage.

So, "resistance" always means 1/2 damage in 5e? 

Yep! Here is the relevant section from the basic rules:

If a creature or an object has resistance to a damage type, damage of that type is halved against it. If a creature or an object has vulnerability to a damage type, damage of that type is doubled against it.

Resistance and then vulnerability are applied after all other modifiers to damage. For example, a creature has resistance to bludgeoning damage and is hit by an attack that deals 25 bludgeoning damage. The creature is also within a magical aura that reduces all damage by 5. The 25 damage is first reduced by 5 and then halved, so the creature takes 10 damage.

Multiple instances of resistance or vulnerability that affect the same damage type count as only one instance. For example, if a creature has resistance to fire damage as well as resistance to all nonmagical damage, the damage of a nonmagical fire is reduced by half against the creature, not reduced by three-quarters.

Does this lessen the triggering damage?

Flex tape cant fix that

Lol I'm just looking at this now, and I can't believe I said that.

What if you normally have a vulnerability to an element, for instance fire?  Does this make is so you just take normal damage or do you get the resistance?  I have a Living Spellbook monster that is vulnerable to fire but has this at their disposal.  

Weird question about this spell. The description does not specify where the damage has to come from to trigger the reaction, just that you can use it against elemental damage.

If I was feeling cheeky, could I technically activate this spell by doing something like running through a campfire or a bit of acid?

As far as I can tell, there's nothing that says I can't do it. Though it does kind of ruin the intended dramatic effect of absorbing part of a fireball or lightning bolt, where instead I stick my hand in the campfire to gain fire resistance and some extra damage.

Quote from Jo_Schway >>

When you take a reaction, you can't take another one until the start of your next turn. This means that you can't cast absorb elements in response to two separate damage types before the start of your next turn. Say you take fire damage from a fire elemental and then cold damage from a frost salamander. After being hit by the fire elemental you could cast absorb elements, granting you resistance to fire damage until the start of your next turn. However, if the frost salamander then hits you with cold damage before the start of your next turn, you can't cast the spell in response to that, as you've already used your reaction. Then your next melee attack will do an extra 1d6 fire damage, unless the spell was cast at a higher level.

 Yes, and this has an odd side effect. If you cast this during your turn, like say a held action fireball damages you, you could then attack with your action or w/e means during that same turn and the extra damage wouldn't apply. You'd have to wait for your next turn.

Why is this an acid spell?

no it does not

I can't see all the damage types

Do you have to take the reaction BEFORE you know how much damage? 

I assume this would be at the discretion of the DM....