98 elantra will not start and headlights dont work

If you have a second key, try that one. Sometimes 1 key will unlock, 1 key will start. If not it would be the anti theft or security system disabling the ignition module. Which is why it won't even try to turn over.

I am thinking that what you experienced is your alternator going out. You will have to have that checked which any auto parts store can do that for you. You will have to fully charge your battery after you replace the alternator.

Normally this condition is the result of a poor body ground connection. Testing for this can be deceiving. At the static(nothing on) condition, testing can show a good ground. However when a circuit is excited, it has a determined resistance and a set current flow. If the ground connection to this or a branch circuit is loose, corroded, or broken wire. This will allow just enough connection to show as being good, but not good enough to complete the circuit with the required amount of connection when energized.

Have you tried jumping the car yet? What have you tried so far? I would get someone to jump it real quick. Theres other ways to see if battery is dead but a quick way is to get a jump then tell us what happens. Good luck-

maybe a starter or one of your sensors mass air flow crankshaft maybe even spark plugs need more information

Is it the illumination lights? If so, that sounds like a bad headlight switch-when you put the park lights on (first click), it turns on the dash illumination lights.
If it is warning lights or other lights on the dash, it could be a bad ignition switch.

Used parts such as starters and altinators don't last. It might **** but it sounds like you need to buy a new starter,altinator, and battery. Or just start with buying one at a time.

try car to car boost-battery charger may not be working correctly or set on low amp charge -interior lights and dash may all light but battery may not be strong enough to energize starter have battery tested if battery good than check for power to the starter if power-- starter may be shot can remove also and have tested at most auto stores free if no power battery -wiring-or connection issue would need to test fuse panel-ignition switch and starter solenoid

thry new battery or know good one sounds like the some cells on that battery are collaps donat start the car with the carger on high this will make the voltage regulator crazy and the light will flicker

The wiring diagrams for the 95 Accent do not show any OEM (original equipment manufacture) 'anti-theft' systems.... this does not preclude the possibility that an After Market system was installed.