LTspice: Adding Third-Party Models
LTspice supplies many device models to include discrete like transistors and MOSFET models.
Nevertheless, there are also many third-party models from manufacturers that are available that you could add to your LTspice IV circuit simulations.
These third-party SPICE models are described with the .MODEL and .SUBCKT statements.
Models given as .MODEL statements are for intrinsic SPICE devices like diodes and transistors, whereas models given by .SUBCKT statements define the component by a collection of circuitry of intrinsic SPICE devices.
This video provides an overview of how to add a third-party .MODEL statement for an intrinsic SPICE device and how to add and create a symbol for a third party .SUBCKT statement to LTspice IV.