How to Make Loading Bar in Unity

The loading bar is a convenient visual design for determining how much is left to load the game

Steps

Create script LoadingBar.cs

using System.Collections;
using TMPro;
using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEngine.UI;

public class LoadingBar : MonoBehaviour
{
    [SerializeField] private Slider _slider;
    [SerializeField] private TMP_Text _load;

    private void Start()
    {
        StartCoroutine(LoadScene());
    }

    private IEnumerator LoadScene()
    {
        AsyncOperation operation = SceneManager.LoadSceneAsync(1);
        operation.allowSceneActivation = false;

        while (!operation.isDone)
        {
            float progress = Mathf.Clamp01(operation.progress / .9f);
            _slider.value = progress;
            _load.text = $"{progress * 100}%";

            if (progress == 1)
            {
                _load.text = "Press [Space] to start";

                if (Input.GetKeyDown(KeyCode.Space))
                {
                    operation.allowSceneActivation = true;
                }
            }

            yield return null;
        }
    }
}