Molecular dynamics (MD) simulation has been widely used in materials research as a tool to demonstrate atomic and molecular interactions from which many important materials properties can be obtained. This book is a tutorial; it intends to assist students and researchers to begin their journey in MD simulations by using the Large-Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). Chapter 1 includes system preparation and introduces the steps of MD simulation. The Appendix includes 11 calculation examples from solids to fluids and property calculation to behavior analysis, each offering detailed problem descriptions, program selection, step-by-step procedures, input code and explanations, important data sheet information, and output demonstrations. We hope this book can give readers an easy and enjoyable start. Enjoy the reading and practice!