Strength: A major strength of fire is its form. Due to having a non-solid form, it is difficult to counter through blocking. For example, even fire were used to attack someone's face, and they tried to block with their arms, they would still receive the same amount of severe damage. Fire can be extremely powerful and difficult to counter for anyone, with the stronger ranked techniques packing great size. Element wise, fire is strong against wind, as the wind would exhaust itself and fuel the fire to an extent.
Weaknesses: A weakness of fire is that it is rather one dimensional. Most of the usages are simply shooting fireballs or firestreams, without much variation between the techniques. Element wise, it is weak to water, as water would quench the flames.
Kekkei Genkai that use fire include Blaze Release, Lava Release, Scorch Release and Steam Release.