Resistance
All monsters in Hell difficulty have 50 percent physical resistance, and so these monsters take only half damage from physical attacks. Monsters in Normal and Nightmare difficulty have no base physical resistance and take full damage from all physical attacks. Melee characters can use special abilities that do elemental damage to do additional damage to these monsters. Ranged characters primarily do elemental damage; even Amazons that use bows have bow attacks that launch arrows with magic, fire or cold damage.
Immunity
Randomly-generated unique monsters and groups of champions can have the ̶0;Immune to Physical̶1; bonus. Monsters with this ability are completely immune to physical damage. Ghostly champions appear to have the Immune to Physical ability, but actually have 80 percent physical resistance and so receive 20 percent of the physical damage you deal. Some unique monsters have an immunity to different types of elemental damage in addition to a physical immunity.
Fighting
Barbarians have the Berserk ability, which converts physical damage into magical damage. Paladins can use their Vengeance ability, which adds additional magic damage to their attacks. Weapons that have fire, cold, lightning or poison damage and charms that add elemental damage when held in your inventory can help. Hirelings with magical attacks, such as the Act 3 mage mercenaries, can aid a melee character with few magic attacks.
Amplify Damage
A Necromancer̵7;s Amplify Damage curse can make enemies more vulnerable to physical damage. It lowers physical resistances and removes the Immune to Physical ability from monsters. Amplify Damage reduces a monster̵7;s physical resistances by 100 percent, resulting in a physical resistance of negative 50 percent when used on Hell monsters. Hell monsters with this curse receive 50 percent extra physical damage. Even rank one of Amplify Damage will have this effect; higher ranks of Amplify Damage just have a higher radius and longer duration.