Define User model (in models folder)

user.js

module.exports = function(sequelize, Sequelize) {
   const User = sequelize.define('user', {
       id: {
           autoIncrement: true,
           primaryKey: true,
           type: Sequelize.INTEGER
       },
       firstname: {
           type: Sequelize.STRING,
           notEmpty: true
       },
       lastname: {
           type: Sequelize.STRING,
           notEmpty: true
       },
       email: {
           type: Sequelize.STRING,
           unique: true,
           notEmpty: true,
           validate: {
               isEmail: true
           }
       },
       password: {
           type: Sequelize.STRING,
           allowNull: false
       },
   });

   return User;
}