I know gyarados was made water/flying because being water/dragon in gen I meant it would've had no weaknesses (since the only dragon-type moves at the time did set damage), but it should have been retyped later on. I guess they didn't want to do it gen II since dragon moves were still rare to have on people's teams, and by the time more dragon moves were introduced people got really used to gyarados having flying as its secondary typing. oh wells
lucario being steel type is still odd to me too!
Lucario black shoulder armor is made of orichalcum, an ancient, mythical metal (‘Lucario’ is the Japanese syllables reversed). Mega Gyarados should've been Water/Dragon type, though.