Elemental Weapon

Source: Player's Handbook

Level 3 Transmutation (Artificer, Druid, Paladin, Ranger)

Casting Time: Action
Range: Touch
Components: V, S
Duration: Concentration, up to 1 hour

A nonmagical weapon you touch becomes a magic weapon. Choose one of the following damage types: Acid, Cold, Fire, Lightning, or Thunder. For the duration, the weapon has a +1 bonus to attack rolls and deals an extra 1d4 damage of the chosen type when it hits.

Using a Higher-Level Spell Slot. If you use a level 5–6 spell slot, the bonus to attack rolls increases to +2, and the extra damage increases to 2d4. If you use a level 7+ spell slot, the bonus increases to +3, and the extra damage increases to 3d4.