What is the duty of the trial court to instruct the jury on the controlling legal principles applicable to a case?

"The general rule is that 'it is the responsibility of the trial court to instruct the jury on the controlling legal principles applicable to a case....' [Citation.]" (Wank v. Richman & Garrett (1985) 165 Cal.App.3d 1103, 1113, 211 Cal.Rptr. 919.) The parties are " 'entitled to have every theory of [their] case submitted to the jury in accordance with the evidence [citations], and the trial court must, when requested, instruct on all vital issues involved.' " However, " '... an erroneous, misleading or incomplete instruction may be refused by the court, and ... the latter is under no duty to modify such instruction or give others in its place, " 'as long as the jury is properly instructed as to the law of the case.' " [Citations.]' " (Ibid.)