From the RuneScape Wiki, the wiki for all things RuneScape

Members only?	No, except for White and Dragon
Highest Melee stat	Slash
Lowest Melee stat	Crush
Strength bonus?	No

A Med helm can be worn in the Headwear Slot. Those offer lesser protection then their Full helmet counterparts, but may be used by mages and rangers as they do not penalise ranged or magic bonuses. Players do not usually wear them however, often choosing a Full helm to take advantage of the significantly greater defensive bonuses, despite the slight mage and range attack penalties.

Normal med helms

• Bronze med helm
• Iron med helm
• Steel med helm
• Black med helm
• White med helm
• Mithril med helm
• Adamant med helm
• Rune med helm
• Dragon med helm

Special med helms

• Crab helmet
• Dharok's helm
• Decorative helm
• Khazard helmet
• Gold helmet