Could you elaborate a Halfling who just wants to keep his friends safe sounds familiar
Well as others as illustrating, it's difficult to build the traditional MMO tank/defender role in 5E. There isn't a simple "grab aggro" mechanic. But another way to be a "defender" is make a character that can soak a ton of damage, incredibly difficult to kill, and can offer some control to the battlefield. The halfling sword & board barbarian is one of those characters:
AC: It's not too hard for a Stout halfling to get to 16 Dex and Con. With a shield, that gives you AC 18 early on.
Hp: d12 Hit Dice, and with Bear Totem you take half damage against everything except psychic damage.
Saves: This is where it gets nutty. Danger Sense gives you advantage against any effects you can see. Halflings have advantage against fear and poison. Plus halflings reroll 1's. Plus, if you make a Dex save, you take no damage because of Shield Master. And if you do fail, you take a quarter damage because of Bear Totem.
For icing on the cake, Shield Master also lets you knock enemies prone every turn and you can make through enemy spaces as a halfling.
So basically you have a ton of hit points, take half (or no) damage almost much all the time, have advantage on a ton of saves, and can move around the battlefield with ease. One of the most fun characters I've ever played. I played him with reckless abandon. I would run through the battlefield and engage the most dangerous opponent or enemy spellcaster. I would "defend" my party by being the most obnoxious combatant on the battlefield. Also makes for a fantastic scout, chest and door opener,
You do trade some damage output but it's still decent once you get your Str to 16 and Extra Attack. Oh, just watch out for spells like Suggestion.