DISCLAIMER: I do not own Dragon Ball Z or Marvel Comics.

Chi-Chi finished making breakfast, and stood up, allowing Gohan to eat. Gohan's one bowl looked ridiculous next to the ten bowls that were waiting for Goku.
"Goku!" Yelled Chi-Chi. "Get down here now!"
When there was no answer, Chi-Chi shrugged. "Come down here or I'll give you food to Vegeta!"
As she finished speaking, there was a flash of movement, and Goku sat at the table, dressed only in pants, and rapidly eating. Chi-Chi smirked. "I'll be sure to remember that threat."

In the sky, Iron Man flew through the air. "So tell me, Pepper. We're here looking for a guy with lots of explosives?"
Pepper's response was very indignant. "Don't be stupid, Tony. We're looking for a man named Goku. SHIELD wants to question him."
Tony rolled his eyes. "Yeah, Fury probably just wants the land cleared so he can use it for a secret base. I trust that guy as far as you could throw him."
Tony slowed down, and hovered in the air. "That's the house. All right, wish the poor guy luck. I'm dropping in unannounced."

Goku was still eating when he heard the sound of some sort of engine. He then looked up in shock as a red suit made of metal dropped in through the roof. Iron Man floated over Goku, and folded his arms. "Hey you. We got something to discuss."
Before Goku could respond, Chi-Chi ran up to Iron Man and started hitting him.
"I'll tell ya what we gotta discuss! You just put a hole in my house, and you even interrupted breakfast! I'm gonna kick your butt!"

Goku watched, amused, as Chi-Chi kicked Iron Man repeatedly, not damaging the armour at all, but still causing indignant comments to come from Iron Man. Goku then stood up and moved over, getting between them, only to receive a slap from Chi-Chi.
"Ow! Chi-Chi, what was that for?"

Several hours later, Chi-Chi had finally calmed down. Goku and Iron Man stood outside, and were focusing on each other.
"So, what's up? Something the matter?"
Iron Man shrugged. "I was told to investigate here by SHIELD. A job I had to do."
Iron Man's helmet suddenly spoke to him in Nick Fury's voice. "You found him. Good. He's not hostile, but we need you to find out just how strong he is. Can you do that?"
Iron Man shrugged. "Sure. Whatever, Fury. You ever considered doing these things yourself, Fury?"
Iron Man looked up at Goku. "Hey, the slimy guy who sent me here wants me to fight you to see how strong you are. You cool with that? If you're not, I can tell him to stuff it."
Goku nodded. "Okay. I could use some training. Come on. I know a good place."

Goku and Iron Man rapidly flew to the field Goku was thinking of, and the two then faced each other. Goku declared the start, and the two charged, each of them taking to the air. The two of them collided, and Goku sent Iron Man hurtling back. Iron Man recovered rapidly, and flew at Goku again, punching him and knocking him back. Goku then fired a Ki blast at Iron Man, sending him flying through the air. Inside the suit, Tony Stark rapidly checked the information he was being sent.
"Energy composition: unknown, but of clearly earthly structure. It reads as similar to static electricity and also to nuclear energy. Likely source: Ki. Damage: Moderate. Physical strike was powered more by speed than anything else, and hit with a lot of force. Damage: Light."

Goku flew into Iron Man, collecting him and flying into the sky with him. Goku rained blows on Iron Man, bending the armour out of shape. Iron Man released the flares he carried, as well as releasing a burst of repulsor energy, the heat from the flares leaving painful burns on Goku's arms and chest. Iron Man flew upwards, Goku letting go of his opponent and quickly blowing on his hands to cool them down after the repulsor blast heated up his fingers. Goku then fired a Ki blast that clipped Iron Man in the shoulder, stripping away a top layer of metal from the shoulder of his suit and sending him spinning. Still shaking himself to put out the embers on his clothing, Goku used Instant Transmission to appear behind Iron Man, and swung his foot at him. To his surprise, Iron Man blocked the kick despite not looking at Goku, before firing a blast from his repulsors which sent Goku flying, sporting some more painful burns. Iron Man sent a missile at Goku, but Goku caught it with his hand, throwing it to one side where it exploded on the side of a cliff. Goku blew on his hand, still slightly bothered by the burns from the flares, before returning his attention to Iron Man.

Goku then powered up to Super Saiyan, deciding to get serious. He fired a Ki beam at Iron Man, which Iron Man barely dodged, before Goku slammed into Iron Man, driving him down to the ground. Iron Man started to struggle, barely hearing his suit telling him that the damage levels were now critical due to the various weapons being made unstable by the earlier barrage of strikes from Goku. Goku tore the mask off and raised his fist, as if he were about to slam his fist straight through Tony Stark's head. Just as it seemed as if he would, he then lowered his hand, before pulling Tony to his feet and steadying him by gripping his shoulders.
"That was fun. You ain't bad. You hungry? Breakfast's ready and waiting."

Analysis:

Goku has almost every advantage in this fight. His strength is greater, seeing as his top strength feat was 20,000 tons with a guarantee that his stronger forms are higher, while Iron Man's strength is stated as being 1000 tons, and most of his feats are around the 100 ton mark. Goku has the edge in speed, since both are relativistic in flight and have similar reactions, but Goku's attacking speed is higher since he can casually catch a stream of bullets. Skill is on Goku's side since he has masterful skills in literally dozens of martial arts as well as a life time of fighting experience and an ability to learn new moves on the fly. Durability is also in Goku's favour, since he gets slammed through buildings, islands and bedrock with little damage, while Iron Man mainly tanks missiles, and is often shown to take great damage from blows of that calibre, such as when Thor or Hulk hits him.

Goku will be hurt by Iron Man's flares since he's shown a few times that sheer heat can hurt him and flares are burning magnesium. This gives Iron Man one advantage apart from being able to survive in space more effectively and being more intelligent, but really these things don't mean much, since Goku would never go to space and if Iron Man does Goku can just start firing blasts, Stark being smarter is useful, but with Goku being that much more efficient in battle situations it gets balanced out. Iron Man being able to hurt Goku with the flares and heat attacks along with his higher intellect gives Iron Man a means to fight back effectively, but it's nowhere close to enough to balance out Goku's advantages.