YouTube is a wonderful place for research. There are many great channels to learn about firearms, mêlée weapons, and unarmed combat for your stories (or self-defense).
I tend to focus on gritty and not entertaining combat (as described in Writing Fight Scenes by Rayne Hall) so I’m always looking for new ideas for combat scenes. In my current story Portal, I have several characters that use bladed weapons including knives, daggers, and long swords. One character (Scimitar) can even shape his upper extremities into metal weapons. Some heroes might shun firearms (looking at you, Dark Knight) but that doesn’t mean a good blade is worthless in a gun fight. In a close quarter battle (CQB), large weapons like rifles and long swords are often a hindrance and can offer a deadly opportunity for the creative hero or villain with a short blade.
It is easy to find great entertaining combat using swords, just go watch The Empire Strikes Back. But what if you want a more realistic look? Here’s YouTube channel scholagladiatoria explaining why stage combat would get you killed in a real fight.