I have a dog with epilepsy!
From what you've said about Metacam, I'd keep my fingers crossed it was a one-off but be prepared for another, just in case.
Things that are useful to know in case of seizure:
- stay very calm and keep noise/light to a minimum. Stimulation can prolong the seizure.
- time the seizure - anything longer than 5 minutes and you should get vet advice. Most seizures are over within 1 to 4 minutes although they will feel longer when you are witnessing them
- Google/research Ocular Compression, plus the use of ice packs as a technique for minimizing seizures. Ocular compression works very well with my girl.
Going forward, if needed, you might want to check diet (low carb/glutamate and as fresh as possible seems to be better), and look into MCT Oil, CBD Oil, and probiotics. People have varying results but all of these things work to minimize seizures for some dogs. There is a lot of research on Canine Epilepsy at the moment so it helps if you can find a vet with an active interest. A veterinary neurologist is worth using in the long term.
Lastly, keep a seizure diary and record any obvious seizure activity. Include any 'odd' behaviour - clinginess, anxiety, fly-snapping, muscular jerks, facial twitches which are unusual. It will all help your vet to work out what's best.
Good luck with this - it IS terrifying, but it does get easier. Here's hoping you don't have another.