You can only burn one spell slot on a given attack for divine smite. Once you get more than one attack per turn you can burn one slot on each attack. Additionally, you can use your bonus action to cast a smite spell, then attack and burn another slot on divine smite.
As Lunali said you can burn a spell slot per an attack and another spell slot for a bonus action spell. This gives you a total of 3 spell slots used per around from level 5 onwards.
You can burn as many spell slots as you have attacks and bonus actions. So if you're hasted that's 6 spell slots in a turn.
At the most if you're multiclass fighter with action surge and hasted this can be a total of 9 spell slots used in a turn. Or over half of your spells slots in one turn.
Oops yeah my bad. For what ever reason went off what critical role does.
That being said though haste combined with action surge is still 6 spell slots. Which is about half your spell slots. And no you dont need to use a bonus action attack to do this. A spell smite spell is cast as a bonus action on top of divine smites.
When you crit on an attack roll the damage your weapon deals is doubled (I think that is how it works). Does this doubled damage effect from the crit carry over to the smite as well or is the double damage only on the weapon roll?
Also, playing as Sorcerer with a level in Paladin, I have access to metamagic. Is there a way to use metamagic to change the effects? (Empower metamagic to change some of the dice rolls, etc?)
When you crit on an attack roll the damage your weapon deals is doubled (I think that is how it works). Does this doubled damage effect from the crit carry over to the smite as well or is the double damage only on the weapon roll?
Also, playing as Sorcerer with a level in Paladin, I have access to metamagic. Is there a way to use metamagic to change the effects? (Empower metamagic to change some of the dice rolls, etc?)
All damage dice rolled as part of the same attack are doubled, so divine smite, sneak attack, extra damage from weapons, etc. Abilities that add a flat amount (ability bonus, great weapon master) or that require a second check (poison) do not get doubled.
All of the metamagics require that you cast a spell to use their effect, so they don't work with divine smite. If you use empower on a smite spell, you will only be able to reroll the dice that are part of the spell.
Is it possible to burn more than one spell slot at a time using the Divine Smite ability?
You can only burn one spell slot on a given attack for divine smite. Once you get more than one attack per turn you can burn one slot on each attack. Additionally, you can use your bonus action to cast a smite spell, then attack and burn another slot on divine smite.
As Lunali said you can burn a spell slot per an attack and another spell slot for a bonus action spell. This gives you a total of 3 spell slots used per around from level 5 onwards.
You can burn as many spell slots as you have attacks and bonus actions. So if you're hasted that's 6 spell slots in a turn.
At the most if you're multiclass fighter with action surge and hasted this can be a total of 9 spell slots used in a turn. Or over half of your spells slots in one turn.
Haste only gives you a single extra attack, so 4 slots in a turn if you are hasted at level 5 and are fighting with two weapons.
Oops yeah my bad. For what ever reason went off what critical role does.
That being said though haste combined with action surge is still 6 spell slots. Which is about half your spell slots. And no you dont need to use a bonus action attack to do this. A spell smite spell is cast as a bonus action on top of divine smites.
When you crit on an attack roll the damage your weapon deals is doubled (I think that is how it works). Does this doubled damage effect from the crit carry over to the smite as well or is the double damage only on the weapon roll?
Also, playing as Sorcerer with a level in Paladin, I have access to metamagic. Is there a way to use metamagic to change the effects? (Empower metamagic to change some of the dice rolls, etc?)
All damage dice rolled as part of the same attack are doubled, so divine smite, sneak attack, extra damage from weapons, etc. Abilities that add a flat amount (ability bonus, great weapon master) or that require a second check (poison) do not get doubled.
All of the metamagics require that you cast a spell to use their effect, so they don't work with divine smite. If you use empower on a smite spell, you will only be able to reroll the dice that are part of the spell.
All Dice Rolled on a Crit for damage are doubled regardless of the cause of the damage.
No meta magic does not work on Divine Smite. This is because Devine Smite IS NOT a spell, it's an ability.
Meta magic would work on Smite Spells like thunderous smite, wrathful smite, etc.