Como el gato al olor de las sardinas
 

This is a saying meaning that somebody is around something or somebody because he has an strong interest in somebody/something
Ia there an expression in English too?

"Sticks to him/her like glue." Here someone is always with the other person for whatever reason. Most likely socially positive.

Negatively, perhaps "hanger's on." Here the people or objects have no relationship. Only a desire by someone to be associated with their object of affection. "Hanger's on" are probably trying to get close to the object for their own personal gain.

I'm also older, so maybe there is better slang the younger folks use.

Like stink on a pig.
Like a hobo on a hotdog.

There are many more.

There are a few very vulgar terms in English, but right now I can't think of any commonly used ones that aren't vulgar.

Here are the ones I can think of now:
Like files on sh..
Like stink on sh..

PS I just remembered one that isn't vulgar and is common;:Like bees to honey

I think the closest is hangers on can you give me an example

A hanger on may be what you are looking for, but the saying like bees to honey really resembles como el gato al olor de las sardinas.

A sentence with hanger on is: I think John is a real hanger on. He's always asking questions like he's using me so he can get ahead.

Example of bees to honey: The shoppers came to the store like bees to honey when they heard about the big sale.