When he think of angels..... He think goodness, love and kindness, angels are mostly associated the beauty anything good. They are considered in many cultures so what makes these spirits so well known in almost every culture.
In most religions they believe that angels are spiritual beings that serve the creator of the heavens. Even though scientific research has never proved it or not successfully tested it, some believe that “just because he can’t something doesn’t mean it doesn’t exist”. Which I feel happens to have some truth not everything he sees is true and everything he doesn’t see isn’t always false. Example social media if he has a friend that sent a text telling him that there is a herd of cattle on the road and it’s blocked even though he haven’t seen the herd he would probably believe him or if the news gave a weather forecast stating that it would be extremely cold the next day he would probably get warm clothes for the morning before work the next day and he didn’t see the cold but believed.
If you don’t believe in angels then here are some words that might make sense, humans might not be perfect and our behaviour might be a little abrupt at times but each of have an angel within ourselves in way mean we still goodness, kindness and beauty, even the most devilish people who we might think are the worst person ever still might have a good side or a good conscious. Just like we all have bad conscious too but we shall save it for another day.
Here are some links you might find interesting:
the link below shows videos of existence of angels you can decide for yourself if its a reality or not
https://familyshare.com/26397/top-5-pieces-of-evidence-that-prove-angels-exist
the other links are reading pieces which I found very informative and used them as a reference