You can cast polymorph, polymorph any object, shapechange, and divine power. You are not likely to have any trouble whatsoever in the melee department; you’re definitely going to do it better than, say... barbarian, bard, duskblade, fighter, favored soul, hexblade, knight, marshal, monk, ninja, paladin, ranger, rogue, samurai, scout, spellthief, or swashbuckler. Clerics will be better, druids will probably be comparable, and you can definitely be much better than crusader, swordsage, and warblade but at least that will take some thought.
One of the primary goals for a melee full-caster is to have buffs up without spending actions on them: have them already-up when the fight starts. Persistent Spell is your friend there, though polymorph any object and shapechange have exceptionally long durations on their own. Divine power will be the primary one you want to get. Arcane Thesis, Easy Metamagic, and Practical Metamagic could make extended persistent divine power a 7th-level spell; you can do far better than that, but it is a 48-hour “you are now a warrior as well as full-caster,” and then you can perform some polymorphing on top of that.
Also, don’t forget your spellcasting. Just because you are good, great even in melee, doesn’t mean you stop being a full-caster. Being a full-caster is far, far more important than having any skill in melee at all, so don’t ignore it.