I have a 98 Chevy Malibu Ls and the ignition won't

SOURCE: 2006 Chevy Impala stuck in park

When you turn ignition on it releases a cable that is attached to the shifter also the shifter has a solenoid attached to it that is released when you step on the brake. Both times that I had the problem of button stuck and cant shift out of park the solenoid was sticking and wouldnt release .

SOURCE: shift gear is locked cannot shift out of park gear

The lever inside the transmission that engages and disengages the "park pal" has most likely come loose or broken altogether. If you are mechanicly inclined and want to verify this you can pull the pan off the trans and look at the park pal and conecting rod to see if it is broken.
Also there is a chance that the stering columb rod that is part of the key switch has broken off and wedged into the shift lever.

Ps. please dont forget to rate the solution. Thanks.

SOURCE: 01 chevy malibu will not shift out of 2nd gear

its possible that your intake manifold is leaking down onto the spark plugs causing the problem to check pull a spark plug out and see if the tip is covered in oil

SOURCE: Impala won't shift into park

to get the key out just set the parking brake and put in neutral, but i agree with the first solution probably bad selector cable or linkage.

SOURCE: My 1994 Chevy Corsica automatic shift stick got

There is a small cable attached to the shift lever that runs up to the ignition switch on the steering column. If it gets stuck, your shift lever won't move out of park and your key can get stuck and you won't be able to pull it out.

Drop the steering column down and detach the cable to free up your shifter and/or key. Make sure to replace it as soon as possible as it is a safety feature.