I'm trying to start a power metal project for fun with a few of my friends. I'm talking about old school power metal bands from the 80's such as Running Wild. I wrote one song that souns awesome imo. But every time I try to write another song, it always starts on the same note or has the same scale. What scale's are used in power metal?

btw: if anyone knows a band that sounds similair to Running Wild please tell me.

Well, most power metal I have heard is either in minor, harmonic minor, or some Middle Eastern sounding key. In my own opinion, its always bad to use major keys because that is what makes power metal corny usually. Try to keep everything fairly fast paced. Tremolo picking riffs is very power metal-ish, as well as guitar harmonies in 3rds. Quickly gallopped rhythm guitar gives a nice headbanging sense to the listener. Hope this helps.

Quite a few power/traditional metal bands use major keys, actually. Take Iron Maiden, for example:

Wasted Years chorus- major key
The Prisoner chorus- major key
Charlotte the Harlot intro- major key (more or less)
Sun and Steel chorus- mixolydian mode
Run to the Hills chorus- mixolydian mode

and so on and so forth. A nice balance of major and minor key choruses would be preferable I should think. The majority of your verses will probably be in minor keys, though.

power metal will use your standard ionian scale (major)
although a dorian in g will work
however i like using power chords and playing three notes of the given "mode" with it gives it a very priest/maiden feel

Thanx guys this really helps. I haven't written anything or whatever but i tried some of this shit out and it sounds good.

To elaborate some.

-Harmonizing in thirds is definitely a power metal tradition, though I, personally HATE it, in melodic death metal too. It is also common in power metal to, at a chorus or climax, just play a given line UP a third, and then up to the 5th in the same key if you wanna raise the tension even more. Classic, safe, epic if not overdone.
-The gallop can be achieved in two ways. Either an 8th note followed by two 16th notes or a triplet (if the piece is primarily triplety, consider using 6/8, this makes 8th notes function like triplets). The former is more overt in its gallopiness. You can actually easily cut between the two from section to section if you want, just as you can cut from an 8th-16th gallop into just a straight constant run or something more hard-rocky.
-Now this is going to come off opinionated but look past it... power metal is one of the most blatantly bland styles to ever exist. Rhythmically and melodically is is DEFINED by its straight-forwardness and diatonic preference (often times triad-based at that) unless a band is adding progressive or thrashy elements, both very common (AND suggested). Playing your songs without swing, chromatics/bluesiness, limiting your tritones, and just playing it safe with the lead runs will not harm your ability to sound like professional power metal.

TWO General Pieces of Writing Advice
-I've found that playing a quarter-note-triplet set chug (dun-dun-dun) can be placed before or after ANYTHING. When in doubt utilize it. Breaks (I suggest of a shreddy guitar-persuasion for power metal) are another easy transitionary tool.
-The classic(al) way to resolve back to the root is to play a dominant (either the in-key chord starting on the 5th note of the scale or the 7th, in a major key) before resolving. If you're in natural minor or using any other key with a minor 7th, it sounds just fine (and very classical-esque) to play the dominants of the MAJOR version of the key; with the major 7th (the leading tone, a half step below the root). If you listen to this, you will IMMEDIATELY recognize the sound.

For any sort of genre:

Listen to it heaps, then pick up a guitar. Once you become familiar with the way riffs are written, chords are done etc. Writing should be a breeze. The best way to write a genre is to listen to that genre heaps.

Listen to stuff that's outside Power Metal but influenced Power Metal for a change-bands like Uriah Heep, Wishbone Ash, Rainbow and Queen.

To combine the previous two pieces of advice: Listen to heaps of Uriah Heep.

sorry.