Yes, slang is part of our lives and definitely we need to learn some slang words to understand when native speakers use them and, why not, with care, use them ourselves?

A very cool slang word is mogollón. Mogollón is basically a big amount of something, oodles of something. It comes from Italian moccobello or Catalan mogobells, which mean a tip, money given to a service.

Here are some examples:

Había un mogollón de gente en la fiesta. Estábamos como sardinas.
There were a lot of people at the party. We were like sardines.

Llegaron en mogollón.
They came in herds.

Vino un mogollón de chicos al partido.
A lot of guys came to the game.

It can also mean a mess, a “zoo”:

Mira qué mogollón hiciste aquí.
Look what a mess you’ve got here.

A causa de los gritos de los vecinos se ha armado un buen mogollón.
There was a riot because of the neighbors’ yelling.

Mogollón can also be used an as adverb:

Eso mola mogollón.
This is very cool.

La quiero mogollón.
I love her a lot.

Me divierto mogollón contigo.
I have a lot of fun with you.

We also have the expression de mogollón which means to do something free of charge, or not paying for it.

Se colaron de mogollón en la fiesta.
They crashed the party.

Si crees que vas a comer de mogollón aquí estás equivocado.
You’re wrong if you think you’re going to scrounge a meal here.

Logró aquel puesto de mogollón.
He wangled that job.

Bueno, por hoy es todo. Nos vemos prontito.