tba (Being written, but major points are already below)
Particularyly in the super-popular The Secret, magnetism is put forth as if it is "magic", something you just generate and it 'mysteriously' attracts things and people to you (often forgetting the idea that you have to do something to get what you want).
In this, people want to be around you - for some reason(s).
Often the reason is more based on emotions than just potential benefits, though they are often related.
For instance, a person may be excited about the potential in his/her life from the potential of learning some wisdom or techniques that will make his/her life better.
Feeling openness, lightness, good feelings from what the person talks about, seeing a person standing straight and powerfully and/or with a great smile or radiance, etc. and etc. generate positive thoughts and emotions that feel good. We are "attracted" to what has us feel better.
If someone is a great example of something we want or enjoy, we feel drawn to that person (actually the emotion generated by ourselves) to experience the benefits.
CONTROL AS A MAGNETISM KILLER
What does a need to control do to your magnetism? Notice that when you try to control something, you tense up because you have to have the right outcome. So you "constrict", which lowers your ability to smile, be light, or be powerful. Your body actually goes into a stress routine, where it even retains fat because it might be needed for survival from the possible threat (the primitive mind doesn't reason well!).
Also, if we try to control people the other people might generate some defensiveness and/or fear of domination, which of course generates in the other person a negative feeling.
We can let go of this need if we learn that we'll be ok even if things don't all turn out as we had hoped. We only need control, in our minds, because we expect life not to turn out, so we think we have to control it.
"MAGNETISM" AROUND GETTING WHAT YOU WANT
This is pretty simple. A mind in fear shifts such that handling the fear is priority and other parts of the body are shut down as not needed (as much, anyway). The higher brain has historically not been useful when attacked by a tiger, so it is shut down.
When we are focusing on opportunity, on creating something great, on some positive emotion or memory, our mind opens (so to speak) and becomes creative plus it is free to use the Reticular Activation to help seek goals, spotting what could be useful.
The "object" is not affected. It is not iron physically attracted by a magnet. It is you that is affected and you that is just more at cause - and it is only a metaphor that you are a "magnet"! You aren't! There is no magic.
There is only pure science and what we need to do, based on that reality, is simply use the tools and ways that work with what we have.
We always need to do something, such as generate a thought, write something, think about something, and do something in the physical world (to get a physical result) where we are applying energy to cause something to happen.
An interesting metaphor here is what happens to your magnetism by adding "positives" into your life, as if they are adding positive energy to the positively-charged side of the magnet. The point here is that you just can't generate magnetism just by "trying" or having it happen in some magical way, you must "do" something. Generating magically is not something that is doable, but, by definition, anything we do must be doable - a defined action that is composed of logical pieces and sequences. For instance, you can "do" listening to a positive CD; you can "do" turning on your MP3 player; you can "do" reading a positive and/or progressive book. (See Positivity Ratio, for a "do" that is guaranteed to produce happiness.)
JOIN A "POSITIVELY CHARGED" POLE TO THE OPPOSITE
If you play with two magnets and put the identically charged ends next to each other there is a force you feel where they are pushed apart. But when you match a positive with a negative pole, they are sucked together by the physical force called magnetism (similar to gravity in a sense).
Since most people "need" something and/or have some negative stuff they want to get rid of, they have their negative pole pointing toward you. If you have the same pole pointing toward them, there is a repulsion or at least no attraction.
So the secret of life, if you want to feel positive attraction (feelings) then you've got to put your positive pole toward them and they'll be attracted to what you have.
But, you say, if two positive poles (positive people) get together wouldn't that be a problem. In this metaphorical context, the two step into the same force field rather than being outside and they generate magnetism and something called synergy.
In synergy, two or more things get together and generate something extra beyond just the sum of the parts that are together. When people are whole in themselves, they do not "need' another person but are choosing instead to align and ally with them. When there is "need" to control the outcome, negative energy is generated.
The classic example is when two people who are incomplete halves get together to form a whole, it doesn't work as there are too many negatives generated in trying to get from the other what one needs and should provide for oneself. When it gets to the point where the other person is simply a bonus rather than a person to cling to to get what we want, then we can have that "great relationship".
But note that the relationship is not like the dysfunctional ones touted in love songs as being wonderful, where one person "completes" the other or saves the other from a life of loneliness, where something is missing (supposedly). Some songs, though, are good such as The Greatest Love Of All - listen to the words and you'll get the idea. (If the link doesn't work just input the title into YouTube.)