explain why metals are good thermal conductors and fluids are poor conductors of heat using the particle model theory of matter.

The reason is because Metals are strong metallic and they make good conductors for electric and heat. While fluids are non metals so they don't produce heat and most of the non metals are brittle and poor conductors.

Metals are an excellent electricity and heat conductor because the metal atoms form a matrix through which the outer electrons can move freely. Instead of orbiting their respective atoms they form a sea of electrons surrounding the positive nuclei of the metal ions that interact.

The force between adjacent particles is strong, making heat transfer by collision the most efficient. The particles in liquid can move around within it, which means that the force between particles is not as strong (Fig. 5b). Thus liquids are usually poor conductors of heat.